U.S. patent number 10,285,191 [Application Number 15/536,788] was granted by the patent office on 2019-05-07 for method for transmitting uplink channel and wireless device requiring coverage enhancement.
This patent grant is currently assigned to LG Electronics Inc.. The grantee listed for this patent is LG Electronics Inc.. Invention is credited to Daesung Hwang, Yunjung Yi.
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United States Patent |
10,285,191 |
Hwang , et al. |
May 7, 2019 |
Method for transmitting uplink channel and wireless device
requiring coverage enhancement
Abstract
One embodiment of the present specification provides a method by
which a wireless device, to which coverage enhancement (CE) is
applied, transmits an uplink channel. The method can comprise a
step for receiving, by the wireless device, sounding reference
signal (SRS) configuration information for other wireless devices
within a cell. The SRS configuration information can comprise
information on SRS transmittable subframes. The method can comprise
a step for transmitting, by the wireless device, the uplink channel
on symbols except for a final symbol on subframes according to a
reduced format, when the wireless device transmits the uplink
channel on the subframes directed by the subframe information
within the SRS configuration information for other wireless
devices.
Inventors: |
Hwang; Daesung (Seoul,
KR), Yi; Yunjung (Seoul, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
LG Electronics Inc. |
Seoul |
N/A |
KR |
|
|
Assignee: |
LG Electronics Inc. (Seoul,
KR)
|
Family
ID: |
56126936 |
Appl.
No.: |
15/536,788 |
Filed: |
December 15, 2015 |
PCT
Filed: |
December 15, 2015 |
PCT No.: |
PCT/KR2015/013763 |
371(c)(1),(2),(4) Date: |
June 16, 2017 |
PCT
Pub. No.: |
WO2016/099135 |
PCT
Pub. Date: |
June 23, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170374675 A1 |
Dec 28, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62245297 |
Oct 23, 2015 |
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62204965 |
Aug 13, 2015 |
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62202144 |
Aug 6, 2015 |
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62109076 |
Jan 29, 2015 |
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62093399 |
Dec 17, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
72/1268 (20130101); H04W 72/0413 (20130101); H04L
5/0051 (20130101); H04L 5/0055 (20130101); H04L
5/0094 (20130101); H04W 72/04 (20130101); H04W
72/0446 (20130101); H04L 5/0012 (20130101); H04L
5/0007 (20130101) |
Current International
Class: |
H04L
5/00 (20060101); H04W 72/04 (20090101); H04W
72/12 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2806581 |
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Nov 2014 |
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EP |
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2999140 |
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Mar 2016 |
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EP |
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2014185749 |
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Nov 2014 |
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WO |
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Other References
LG Electronics Inc., "Summary of Offline Discussion on
Clarification of PUSCH Rate Matching with SRS," R1-144485, 3GPP TSG
RAN WG1 Meeting #78bis, Oct. 14, 2014. cited by applicant .
Media Tek Inc., "Discussion on PUCCH for Rel-13 MTC UE," R1-144853,
3GPP TSG RAN WG1 Meeting #79, Nov. 8, 2014. cited by applicant
.
LG Electronics, "Considerations on PUCCH and PUSCH Design for MTC,"
R1-144894, 3GPP TSG RAN WG1 Meeting #79, Nov. 8, 2014. cited by
applicant .
NEC, "Coverage Enhancement for PUSCH," R1-144861, 3GPP TSG RAN WG1
Meeting #79, Nov. 8, 2014. cited by applicant .
3GPP TS 36.211 V10.4.0, Release 10, Dec. 2011. cited by applicant
.
Zte, "Bandwidth reduction for low complexity UEs," 3GPP TSG RAN WG1
Meeting #79, Nov. 17-21, 2014, R1-144815. cited by
applicant.
|
Primary Examiner: Mizrahi; Diane D
Attorney, Agent or Firm: Dentons US LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the National Stage filing under 35 U.S.C. 371
of International Application No. PCT/KR2015/013763, filed on Dec.
15, 2015, which claims the benefit of U.S. Provisional application
Ser. No. 62/093,399 filed on Dec. 17, 2014, Ser. No. 62/109,076
filed on Jan. 29, 2015, Ser. No. 62/202,144 filed on Aug. 6, 2015,
Ser. No. 62/204,965 filed on Aug. 13, 2015, and Ser. No. 62/245,297
filed on Oct. 23, 2015, the contents of which are all hereby
incorporated by reference herein in their entirety.
Claims
What is claimed is:
1. A method for transmitting a physical uplink shared channel
(PUSCH), the method performed by a wireless device and comprising:
receiving information on a cell-specific sounding reference signal
(SRS) subframe configured for any other user equipment (UE),
wherein the wireless device is configured to not transmit the SRS,
determining whether a subframe for transmitting a PUSCH includes a
symbol overlapping an SRS symbol in the cell-specific SRS subframe;
and mapping the PUSCH to one or more symbols of the subframe
including the symbol overlapping the SRS symbol, wherein the symbol
overlapping the SRS symbol is not used by the wireless device,
which is configured to not transmit the SRS.
2. The method of claim 1, further comprising: determining whether
the subframe for transmitting the PUSCH is the cell-specific SRS
subframe.
3. A method for transmitting a sounding reference signal (SRS), the
method performed by a wireless device and comprising: determining
whether a first frequency band in a subframe n is not included
within a second frequency band in a subframe n+1; when the first
frequency band in the subframe n is not included within the second
frequency band in the subframe n+1, determining that the SRS is to
be dropped from the subframe n; when the first frequency band in
the subframe n is included within the second frequency band in the
subframe n+1, transmitting the SRS in the subframe n.
4. The method of claim 3, wherein the wireless device is configured
for coverage enhancement or to use a reduced bandwidth.
5. The method of claim 3, further comprising: hopping from the
first frequency band to the second frequency band.
6. The method of claim 3, wherein a physical uplink shared channel
(PUSCH) is transmitted in the subframe n.
7. A wireless device for transmitting a physical uplink shared
channel (PUSCH), the wireless device comprising: a transceiver
configured to receive information on a cell-specific sounding
reference signal (SRS) subframe configured for any other user
equipment (UE), wherein the wireless device is configured to not
transmit the SRS, and a processor, operatively coupled to the
transceiver, wherein the processor is configured to: determine
whether a subframe for transmitting a PUSCH includes a symbol
overlapping an SRS symbol in the cell-specific SRS subframe; and
map the PUSCH on one or more symbols of the subframe including the
symbol overlapping the SRS symbol, wherein the symbol overlapping
the SRS symbol is not used by the wireless device which is
configured to not transmit the SRS.
8. The wireless device of claim 7, wherein the processor is further
configured to: determine whether the subframe for transmitting the
PUSCH is the cell-specific SRS subframe.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to mobile communication.
Related Art
3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution)
that is an advancement of UMTS (Universal Mobile Telecommunication
System) is being introduced with 3GPP release 8. In 3GPP LTE, OFDMA
(orthogonal frequency division multiple access) is used for
downlink, and SC-FDMA (single carrier-frequency division multiple
access) is used for uplink. The 3GPP LTE adopts MIMO (multiple
input multiple output) having maximum four antennas. Recently, a
discussion of 3GPP LTE-A (LTE-Advanced) which is the evolution of
the 3GPP LTE is in progress.
As set forth in 3GPP TS 36.211 V10.4.0, the physical channels in
3GPP LTE may be classified into data channels such as PDSCH
(physical downlink shared channel) and PUSCH (physical uplink
shared channel) and control channels such as PDCCH (physical
downlink control channel), PCFICH (physical control format
indicator channel), PHICH (physical hybrid-ARQ indicator channel)
and PUCCH (physical uplink control channel).
Meanwhile, in recent years, communication, i.e., machine type
communication (MTC), occurring between devices or between a device
and a server without a human interaction, i.e., a human
intervention, is actively under research. The MTC refers to the
concept of communication based on an existing wireless
communication network used by a machine device instead of a user
equipment (UE) used by a user.
Since the MTC has a feature different from that of a normal UE, a
service optimized to the MTC may differ from a service optimized to
human-to-human communication. In comparison with a current mobile
network communication service, the MTC can be characterized as a
different market scenario, data communication, less costs and
efforts, a potentially great number of MTC apparatuses, wide
service areas, low traffic for each MTC apparatus, etc.
Since the MTC device may exist at a location where the signal is
weak, performance may deteriorate when the base station estimates
the channel by using a reference signal transmitted by the MTC
device, for example, a demodulation reference signal (DMRS).
Meanwhile, a sounding reference signal (SRS) transmitted by the MTC
device may collide with the SRS transmitted by the existing general
UE.
SUMMARY OF THE INVENTION
Accordingly, the disclosure of the specification has been made in
an effort to solve the problem.
To achieve the foregoing purposes, the disclosure of the present
invention proposes a method for transmitting an uplink channel. The
method may be performed by a wireless device to which coverage
enhancement (CE) is applied. The method may comprise: receiving, by
the wireless device, sounding reference signal (SRS) configuration
information for other wireless devices in a cell, the SRS
configuration information including information on a subframe in
which an SRS is transmittable; and when the wireless device is to
transmit the uplink channel on a subframe indicated by the subframe
information in the SRS configuration information for the other
wireless devices, transmitting, by the wireless device, the uplink
channel on symbols other than a last symbol on the subframe
according to a reduced format.
Even though the wireless device does not transmit the SRS on the
last symbol in the subframe indicated by the subframe information,
the uplink channel may be transmitted only on the symbols other
than the last symbol on the subframe according to the reduced
format.
The uplink channel may be a physical uplink control channel (PUCCH)
or a physical uplink shared channel (PUSCH).
When the uplink channel is the PUCCH, whether the reduced format is
used may be determined according to a higher layer signal.
The SRS configuration information for the other wireless devices
may further include configuration information for simultaneous
transmission of the SRS and hybrid automatic repeat request
(HARQ)-acknowledgement (ACK)/non-acknowledgement (NACK). When the
simultaneous transmission of the SRS and the HARQ-ACK/NACK is
configured on the subframe indicated by the subframe information in
the SRS configuration information for the other wireless devices,
the reduced format may be used.
The uplink channel may be repeatedly transmitted on multiple
subframes according to the coverage enhancement (CE).
The SRS configuration information for other wireless devices in the
cell may be received through the higher layer signal.
When a frequency band in which the wireless device is to transmit
the uplink channel and the frequency band in which the wireless
device is to transmit the SRS are different from each other, the
wireless device may not transmit the SRS on the subframe.
When the frequency band in which the wireless device is to transmit
the uplink channel and the frequency band in which the wireless
device is to transmit the SRS are different from each other, the
transmission of the uplink channel may stop during a time gap
required for changing the frequency band for the SRS
transmission.
In another aspect, to achieve the foregoing purposes, the
disclosure of the present invention proposes a wireless device for
transmitting an uplink channel. The wireless device may be
configured with a coverage enhancement (CE) and comprise: a
transceiver; and a processor controlling the transceiver in
connection with the transceiver. The processor may be configured to
perform: receiving sounding reference signal (SRS) configuration
information for other wireless devices in a cell, the SRS
configuration information including information on a subframe in
which an SRS is transmittable, and when the wireless device is to
transmit the uplink channel on a subframe indicated by the subframe
information in the SRS configuration information for the other
wireless devices, transmitting, by the wireless device, the uplink
channel on symbols other than a last symbol on the subframe
according to a reduced format.
According to the disclosure of the present specification, the
problems of the above-described prior art are solved.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a wireless communication system.
FIG. 2 illustrates the architecture of a radio frame according to
frequency division duplex (FDD) of 3rd generation partnership
project (3GPP) long term evolution (LTE).
FIG. 3 illustrates the architecture of a downlink radio frame
according to time division duplex (TDD) in 3GPP LTE.
FIG. 4 illustrates an example resource grid for one uplink or
downlink slot in 3GPP LTE.
FIG. 5 illustrates the architecture of a downlink subframe.
FIG. 6 is an exemplary diagram illustrating a transmission region
based on the PUCCH formation.
FIGS. 7a and 7b are one example of a subframe in which a DMRS for a
PUSCH is transmitted.
FIG. 8 is a diagram illustrating an environment of heterogeneous
networks of a macro cell and a small cell which may become a
next-generation wireless communication system.
FIG. 9 illustrates one example of machine type communication
(MTC).
FIGS. 10a and 10b are exemplary diagrams illustrating not the
entirety of an uplink system band but a partial subband of the MTC
device.
FIG. 11a is an example of cell coverage enhancement for an MTC
device.
FIG. 11b is an exemplary diagram illustrating an example of
transmitting a bundle of uplink channels.
FIG. 12 is an exemplary diagram illustrating a method for enhancing
a DMRS for demodulating a PUSCH.
FIG. 13 illustrates an example in which a new DMRS for demodulating
the PUSCH is mapped.
FIG. 14 illustrates an example in which the new DMRS for
demodulating the PUSCH collides with the SRS.
FIG. 15 illustrates an example in which an uplink channel
transmitted by the MTC device influences the SRS transmitted by the
legacy UE.
FIG. 16 is an exemplary diagram illustrating one method for
preventing the SRS transmitted by the legacy UE and the PUSCH
transmitted by the MTC device from colliding with each other.
FIG. 17 is an exemplary diagram illustrating one method for
preventing the SRS transmitted by the legacy UE and the PUCCH
transmitted by the MTC device from colliding with each other.
FIG. 18 is a block diagram illustrating a wireless communication
system in which the disclosure of the present invention is
implemented.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
Hereinafter, based on 3rd Generation Partnership Project (3GPP)
long term evolution (LTE) or 3GPP LTE-advanced (LTE-A), the present
invention will be applied. This is just an example, and the present
invention may be applied to various wireless communication systems.
Hereinafter, LTE includes LTE and/or LTE-A.
The technical terms used herein are used to merely describe
specific embodiments and should not be construed as limiting the
present invention. Further, the technical terms used herein should
be, unless defined otherwise, interpreted as having meanings
generally understood by those skilled in the art but not too
broadly or too narrowly. Further, the technical terms used herein,
which are determined not to exactly represent the spirit of the
invention, should be replaced by or understood by such technical
terms as being able to be exactly understood by those skilled in
the art. Further, the general terms used herein should be
interpreted in the context as defined in the dictionary, but not in
an excessively narrowed manner.
The expression of the singular number in the specification includes
the meaning of the plural number unless the meaning of the singular
number is definitely different from that of the plural number in
the context. In the following description, the term `include` or
`have` may represent the existence of a feature, a number, a step,
an operation, a component, a part or the combination thereof
described in the specification, and may not exclude the existence
or addition of another feature, another number, another step,
another operation, another component, another part or the
combination thereof.
The terms `first` and `second` are used for the purpose of
explanation about various components, and the components are not
limited to the terms `first` and `second`. The terms `first` and
`second` are only used to distinguish one component from another
component. For example, a first component may be named as a second
component without deviating from the scope of the present
invention.
It will be understood that when an element or layer is referred to
as being "connected to" or "coupled to" another element or layer,
it can be directly connected or coupled to the other element or
layer or intervening elements or layers may be present. In
contrast, when an element is referred to as being "directly
connected to" or "directly coupled to" another element or layer,
there are no intervening elements or layers present.
Hereinafter, embodiments of the present invention will be described
in greater detail with reference to the accompanying drawings. In
describing the present invention, for ease of understanding, the
same reference numerals are used to denote the same components
throughout the drawings, and repetitive description on the same
components will be omitted. Detailed description on well-known arts
which are determined to make the gist of the invention unclear will
be omitted. The accompanying drawings are provided to merely make
the spirit of the invention readily understood, but not should be
intended to be limiting of the invention. It should be understood
that the spirit of the invention may be expanded to its
modifications, replacements or equivalents in addition to what is
shown in the drawings.
As used herein, `base station` generally refers to a fixed station
that communicates with a wireless device and may be denoted by
other terms such as eNB (evolved-NodeB), BTS (base transceiver
system), or access point.
As used herein, user equipment (UE) may be stationary or mobile,
and may be denoted by other terms such as device, wireless device,
terminal, MS (mobile station), UT (user terminal), SS (subscriber
station), MT (mobile terminal) and etc.
FIG. 1 Illustrates a Wireless Communication System.
As seen with reference to FIG. 1, the wireless communication system
includes at least one base station (BS) 20. Each base station 20
provides a communication service to specific geographical areas
(generally, referred to as cells) 20a, 20b, and 20c. The cell can
be further divided into a plurality of areas (sectors).
The UE generally belongs to one cell and the cell to which the
terminal belong is referred to as a serving cell. A base station
that provides the communication service to the serving cell is
referred to as a serving BS. Since the wireless communication
system is a cellular system, another cell that neighbors to the
serving cell is present. Another cell which neighbors to the
serving cell is referred to a neighbor cell. A base station that
provides the communication service to the neighbor cell is referred
to as a neighbor BS. The serving cell and the neighbor cell are
relatively decided based on the UE.
Hereinafter, a downlink means communication from the base station
20 to the UE1 10 and an uplink means communication from the UE 10
to the base station 20. In the downlink, a transmitter may be a
part of the base station 20 and a receiver may be a part of the UE
10. In the uplink, the transmitter may be a part of the UE 10 and
the receiver may be a part of the base station 20.
Meanwhile, the wireless communication system may be generally
divided into a frequency division duplex (FDD) type and a time
division duplex (TDD) type. According to the FDD type, uplink
transmission and downlink transmission are achieved while occupying
different frequency bands. According to the TDD type, the uplink
transmission and the downlink transmission are achieved at
different time while occupying the same frequency band. A channel
response of the TDD type is substantially reciprocal. This means
that a downlink channel response and an uplink channel response are
approximately the same as each other in a given frequency region.
Accordingly, in the TDD based wireless communication system, the
downlink channel response may be acquired from the uplink channel
response. In the TDD type, since an entire frequency band is
time-divided in the uplink transmission and the downlink
transmission, the downlink transmission by the base station and the
uplink transmission by the terminal may not be performed
simultaneously. In the TDD system in which the uplink transmission
and the downlink transmission are divided by the unit of a
sub-frame, the uplink transmission and the downlink transmission
are performed in different sub-frames.
Hereinafter, the LTE system will be described in detail.
FIG. 2 Shows a Downlink Radio Frame Structure According to FDD of
3rd Generation Partnership Project (3GPP) Long Term Evolution
(LTE).
The radio frame of FIG. 2 may be found in the section 5 of 3GPP TS
36.211 V10.4.0 (2011 December) "Evolved Universal Terrestrial Radio
Access (E-UTRA); Physical Channels and Modulation (Release
10)".
Referring to FIG. 2, the radio frame consists of 10 subframes. One
subframe consists of two slots. Slots included in the radio frame
are numbered with slot numbers 0 to 19. A time required to transmit
one subframe is defined as a transmission time interval (TTI). The
TTI may be a scheduling unit for data transmission. For example,
one radio frame may have a length of 10 milliseconds (ms), one
subframe may have a length of 1 ms, and one slot may have a length
of 0.5 ms.
The structure of the radio frame is for exemplary purposes only,
and thus the number of subframes included in the radio frame or the
number of slots included in the subframe may change variously.
Meanwhile, one slot may include a plurality of orthogonal frequency
division multiplexing (OFDM) symbols. The number of OFDM symbols
included in one slot may vary depending on a cyclic prefix (CP).
One slot includes 7 OFDM symbols in case of a normal CP, and one
slot includes 6 OFDM symbols in case of an extended CP. Herein,
since the 3GPP LTE uses orthogonal frequency division multiple
access (OFDMA) in a downlink (DL), the OFDM symbol is only for
expressing one symbol period in a time domain, and there is no
limitation in a multiple access scheme or terminologies. For
example, the OFDM symbol may also be referred to as another
terminology such as a single carrier frequency division multiple
access (SC-FDMA) symbol, a symbol period, etc.
FIG. 3 Illustrates an Example Resource Grid for One Uplink or
Downlink Slot in 3GPP LTE.
Referring to FIG. 3, the uplink slot includes a plurality of OFDM
(orthogonal frequency division multiplexing) symbols in the time
domain and NRB resource blocks (RBs) in the frequency domain. For
example, in the LTE system, the number of resource blocks (RBs),
i.e., N.sub.RB, may be one from 6 to 110.
Resource block (RB) is a resource allocation unit and includes a
plurality of sub-carriers in one slot. For example, if one slot
includes seven OFDM symbols in the time domain and the resource
block includes 12 sub-carriers in the frequency domain, one
resource block may include 7.times.12 resource elements (REs).
Meanwhile, the number of sub-carriers in one OFDM symbol may be one
of 128, 256, 512, 1024, 1536, and 2048.
In 3GPP LTE, the resource grid for one uplink slot shown in FIG. 3
may also apply to the resource grid for the downlink slot.
FIG. 4 Illustrates the Architecture of a Downlink Sub-Frame.
In FIG. 4, assuming the normal CP, one slot includes seven OFDM
symbols, by way of example.
The DL (downlink) sub-frame is split into a control region and a
data region in the time domain. The control region includes up to
first three OFDM symbols in the first slot of the sub-frame.
However, the number of OFDM symbols included in the control region
may be changed. A PDCCH (physical downlink control channel) and
other control channels are allocated to the control region, and a
PDSCH is allocated to the data region.
The physical channels in 3GPP LTE may be classified into data
channels such as PDSCH (physical downlink shared channel) and PUSCH
(physical uplink shared channel) and control channels such as PDCCH
(physical downlink control channel), PCFICH (physical control
format indicator channel), PHICH (physical hybrid-ARQ indicator
channel) and PUCCH (physical uplink control channel).
FIG. 5 Illustrates the Architecture of an Uplink Sub-Frame in 3GPP
LTE.
Referring to FIG. 5, the uplink sub-frame may be separated into a
control region and a data region in the frequency domain. The
control region is assigned a PUCCH (physical uplink control
channel) for transmission of uplink control information. The data
region is assigned a PUSCH (physical uplink shared channel) for
transmission of data (in some cases, control information may also
be transmitted).
The PUCCH for one terminal is assigned in resource block (RB) pair
in the sub-frame. The resource blocks in the resource block pair
take up different sub-carriers in each of the first and second
slots. The frequency occupied by the resource blocks in the
resource block pair assigned to the PUCCH is varied with respect to
a slot boundary. This is referred to as the RB pair assigned to the
PUCCH having been frequency-hopped at the slot boundary.
The terminal may obtain a frequency diversity gain by transmitting
uplink control information through different sub-carriers over
time. m is a location index that indicates a logical frequency
domain location of a resource block pair assigned to the PUCCH in
the sub-frame.
The uplink control information transmitted on the PUCCH includes an
HARQ (hybrid automatic repeat request), an ACK
(acknowledgement)/NACK (non-acknowledgement), a CQI (channel
quality indicator) indicating a downlink channel state, and an SR
(scheduling request) that is an uplink radio resource allocation
request.
The PUSCH is mapped with a UL-SCH that is a transport channel. The
uplink data transmitted on the PUSCH may be a transport block that
is a data block for the UL-SCH transmitted for the TTI. The
transport block may be user information. Or, the uplink data may be
multiplexed data. The multiplexed data may be data obtained by
multiplexing the transport block for the UL-SCH and control
information. For example, the control information multiplexed with
the data may include a CQI, a PMI (precoding matrix indicator), an
HARQ, and an RI (rank indicator). Or, the uplink data may consist
only of control information.
FIG. 6 Illustrates the PUCCH and the PUSCH on an Uplink
Subframe.
PUCCH formats will be described with reference to FIG. 6.
The PUCCH format 1 carries the scheduling request (SR). In this
case, an on-off keying (OOK) mode may be applied. The PUCCH format
1a carries acknowledgement/non-acknowledgement (ACK/NACK) modulated
in a binary phase shift keying (BPSK) mode with respect to one
codeword. The PUCCH format 1b carries ACK/NACK modulated in a
quadrature phase shift keying (QPSK) mode with respect to two
codewords. The PUCCH format 2 carries a channel quality indicator
(CQI) modulated in the QPSK mode. The PUCCH formats 2a and 2b carry
the CQI and the ACK/NACK.
A table given below carries the PUCCH formats.
TABLE-US-00001 TABLE 1 Total bit Modulation count per Format mode
subframe Description Format 1 Undecided Undecided Scheduling
request (SR) Format 1a BPSK 1 ACK/NACK of 1-bit HARQ, scheduling
request (SR) may be present or not present Format 1b QPSK 2
ACK/NACK of 2-bit HARQ, scheduling request (SR) may be present or
not present Format 2 QPSK 20 In case of extended CP, CSI and 1-bit
or 2-bit HARQ ACK/NACK Format 2a QPSK + BPSK 21 CSI and 1-bit HARQ
ACK/NACK Format 2b QPSK + BPSK 22 CSI and 2-bit HARQ ACK/NACK
Format 3 QPSK 48 Multiple ACKs/NACKs, CSI, and scheduling request
(SR) may be present or not present
Each PUCCH format is transmitted while being mapped to a PUCCH
region. For example, the PUCCH format 2/2a/2b is transmitted while
being mapped to resource blocks (m=0 and 1) of band edges assigned
to the UE. A mixed PUCCH RB may be transmitted while being mapped
to a resource block (e.g., m=2) adjacent to the resource block to
which the PUCCH format 2/2a/2b is assigned in a central direction
of the band. The PUCCH format 1/1a/1b in which the SR and the
ACK/NACK are transmitted may be disposed in a resource block in
which m=4 or m=5. The number (N(2)RB) of resource blocks which may
be used in the PUCCH format 2/2a/2b in which the CQI is transmitted
may be indicated to the UE through a broadcasted signal.
<Uplink Reference Signal>
Hereinafter, an uplink reference signal will be described.
The reference signal is generally transported in sequence. As the
sequence of the reference signal, a predetermined sequence may be
used without a particular limit. As the reference signal sequence,
a sequence (PSK-based computer generated sequence) generated
through a phase shift keying (PSK) based computer may be used.
Examples of the PSK include binary phase shift keying (BPSK),
quadrature phase shift keying (QPSK), and the like. Alternatively,
as the reference signal sequence, a constant amplitude zero
auto-correlation (CAZAC) sequence may be used. Examples of the
CAZAC sequence include a zadoff-chu (ZC) based sequence, a ZC
sequence with cyclic extension, a ZC sequence with truncation, and
the like. Alternatively, as the reference signal sequence, a
pseudo-random (PN) sequence may be used. Examples of the PN
sequence include an m-sequence, a sequence generated through the
computer, a gold sequence, a Kasami sequence, and the like.
Further, as the reference signal sequence, a cyclically shifted
sequence may be used.
The uplink reference signal may be divided into the demodulation
reference signal (DMRS) and the sounding reference signal (SRS).
The DMRS is a reference signal used in the channel estimation for
demodulating a received signal. The DMRS may be associated with
transmission of a PUSCH or PUCCH. The SRS is a reference signal
which the terminal transmits to a base station for uplink
scheduling. The base station estimates an uplink channel through
the received sounding reference signal and uses the estimated
uplink channel in the uplink scheduling. The SRS is not associated
with transmission of the PUSCH or PUCCH. The same type of base
sequence may be used for the DMRS and the SRS. Meanwhile, precoding
applied to the DMRS in uplink multi-antenna transmission may be the
same as precoding applied to the PUSCH. Cyclic shift separation is
a primary scheme that multiplexes the DMRS. In the 3GPP LTE-A
system, the SRS may not be precoded and further, may an antenna
specific reference signal.
The reference signal sequence r.sub.u,v.sup.(.alpha.)(n) may be
defined based on a base sequence b.sub.u,v(n) and a cyclic shift a
by an equation given below.
r.sub.u,v.sup.(.alpha.)(n)=e.sup.j.alpha.nb.sub.u,v(n),0.ltoreq.n<M.su-
b.sc.sup.RS [Equation 1]
In Equation 1, M.sub.sc.sup.RS=m*N.sub.sc.sup.RB
(1.ltoreq.m.ltoreq.N.sub.RB.sup.max,UL) represents the length of
the reference signal sequence. N.sub.sc.sup.RB represents the size
of a resource block represented by the number of subcarriers in the
frequency domain and N.sub.RB.sup.max,UL represents a maximum value
of an uplink bandwidth represented by the multiple of
N.sub.sc.sup.RB. A plurality of reference signal sequences may be
defined by differently applying a which is the cyclic shift value
from one base sequence.
The base sequence b.sub.u,v(n) is divided into a plurality of
groups and in this case, u.di-elect cons.{0, 1, . . . , 29}
represents a group number and v represents a base sequence number
in a group. The base sequence depends on the length
(M.sub.sc.sup.RS) of the base sequence. Each group includes one
base sequence (v=0) in which the length is M.sub.sc.sup.RS with
respect to m of 1.ltoreq.m.ltoreq.5 and includes two base sequences
(v=0, 1) in which the length is M.sub.sc.sup.RS with respect to m
of 6.ltoreq.m.ltoreq.n.sub.RB.sup.max,UL. A sequence group number u
and a base sequence number v in the group may vary depending on a
time like group hopping or sequence hopping.
When the length of the reference signal sequence is
3N.sub.sc.sup.RB or more, the base sequence may be defined by an
equation given below. b.sub.u,v(n)=x.sub.q(n mod
N.sub.ZC.sup.RS),0.ltoreq.n<M.sub.sc.sup.RS [Equation 2]
In the above equation, q represents a root index of a Zadoff-Chu
(ZC) sequence. N.sub.ZC.sup.RS represent the length of the ZC
sequence may be given as a prime number smaller than
M.sub.sc.sup.RS. The ZC sequence having the root index of q may be
defined by Equation 4.
.function..times..pi..times..times..times..times..function..ltoreq..ltore-
q..times..times. ##EQU00001##
In the above equation, q may be given by an equation given below.
q=.left brkt-bot.q+1/2.right brkt-bot.+v(-1).sup..left
brkt-bot.2q.right brkt-bot. q=N.sub.ZC.sup.RS(u+1)/31 [Equation
4]
When the length of the reference signal sequence is
3N.sub.sc.sup.RB or less, the base sequence may be defined by an
equation given below.
b.sub.u,v(n)=e.sup.j.PHI.(n).pi./4,0.ltoreq.n.ltoreq.M.sub.sc.sup.RS-1
[Equation 5]
A table given below shows an example in which .phi.(n) is defined
when M.sub.sc.sup.RS=N.sub.sc.sup.RB.
TABLE-US-00002 TABLE 2 .phi.(0), . . . , .phi.(11) 0 -1 1 3 -3 3 3
1 1 3 1 -3 3 1 1 1 3 3 3 -1 1 -3 -3 1 -3 3 2 1 1 -3 -3 -3 -1 -3 -3
1 -3 1 -1 3 -1 1 1 1 1 -1 -3 -3 1 -3 3 -1 4 -1 3 1 -1 1 -1 -3 -1 1
-1 1 3 5 1 -3 3 -1 -1 1 1 -1 -1 3 -3 1 6 -1 3 -3 -3 -3 3 1 -1 3 3
-3 1 7 -3 -1 -1 -1 1 -3 3 -1 1 -3 3 1 8 1 -3 3 1 -1 -1 -1 1 1 3 -1
1 9 1 -3 -1 3 3 -1 -3 1 1 1 1 1 10 -1 3 -1 1 1 -3 -3 -1 -3 -3 3 -1
11 3 1 -1 -1 3 3 -3 1 3 1 3 3 12 1 -3 1 1 -3 1 1 1 -3 -3 -3 1 13 3
3 -3 3 -3 1 1 3 -1 -3 3 3 14 -3 1 -1 -3 -1 3 1 3 3 3 -1 1 15 3 -1 1
-3 -1 -1 1 1 3 1 -1 -3 16 1 3 1 -1 1 3 3 3 -1 -1 3 -1 17 -3 1 1 3
-3 3 -3 -3 3 1 3 -1 18 -3 3 1 1 -3 1 -3 -3 -1 -1 1 -3 19 -1 3 1 3 1
-1 -1 3 -3 -1 -3 -1 20 -1 -3 1 1 1 1 3 1 -1 1 -3 -1 21 -1 3 -1 1 -3
-3 -3 -3 -3 1 -1 -3 22 1 1 -3 -3 -3 -3 -1 3 -3 1 -3 3 23 1 1 -1 -3
-1 -3 1 -1 1 3 -1 1 24 1 1 3 1 3 3 -1 1 -1 -3 -3 1 25 1 -3 3 3 1 3
3 1 -3 -1 -1 3 26 1 3 -3 -3 3 -3 1 -1 -1 3 -1 -3 27 -3 -1 -3 -1 -3
3 1 -1 1 3 -3 -3 28 -1 3 -3 3 -1 3 3 -3 3 3 -1 -1 29 3 -3 -3 -1 -1
-3 -1 3 -3 3 1 -1
A table given below shows an example in which .phi.(n) is defined
when M.sub.sc.sup.RS=2*N.sub.sc.sup.RB.
TABLE-US-00003 TABLE 3 .phi.(0), . . . , .phi.(23) 0 -1 3 1 -3 3 -1
1 3 -3 3 1 3 -3 3 1 1 -1 1 3 -3 3 -3 -1 -3 1 -3 3 -3 -3 -3 1 -3 -3
3 -1 1 1 1 3 1 -1 3 -3 -3 1 3 1 1 -3 2 3 -1 3 3 1 1 -3 3 3 3 3 1 -1
3 -1 1 1 -1 -3 -1 -1 1 3 3 3 -1 -3 1 1 3 -3 1 1 -3 -1 -1 1 3 1 3 1
-1 3 1 1 -3 -1 -3 -1 4 -1 -1 -1 -3 -3 -1 1 1 3 3 -1 3 -1 1 -1 -3 1
-1 -3 -3 1 -3 -1 -1 5 -3 1 1 3 -1 1 3 1 -3 1 -3 1 1 -1 -1 3 -1 -3 3
-3 -3 -3 1 1 6 1 1 -1 -1 3 -3 -3 3 -3 1 -1 -1 1 -1 1 1 -1 -3 -1 1
-1 3 -1 -3 7 -3 3 3 -1 -1 -3 -1 3 1 3 1 3 1 1 -1 3 1 -1 1 3 -3 -1
-1 1 8 -3 1 3 -3 1 -1 -3 3 -3 3 -1 -1 -1 -1 1 -3 -3 -3 1 -3 -3 -3 1
-3 9 1 1 -3 3 3 -1 -3 -1 3 -3 3 3 3 -1 1 1 -3 1 -1 1 1 -3 1 1 10 -1
1 -3 -3 3 -1 3 -1 -1 -3 -3 -3 -1 -3 -3 1 -1 1 3 3 -1 1 -1 3 11 1 3
3 -3 -3 1 3 1 -1 -3 -3 -3 3 3 -3 3 3 -1 -3 3 -1 1 -3 1 12 1 3 3 1 1
1 -1 -1 1 -3 3 -1 1 1 -3 3 3 -1 -3 3 -3 -1 -3 -1 13 3 -1 -1 -1 -1
-3 -1 3 3 1 -1 1 3 3 3 -1 1 1 -3 1 3 -1 -3 3 14 -3 -3 3 1 3 1 -3 3
1 3 1 1 3 3 -1 -1 -3 1 -3 -1 3 1 1 3 15 -1 -1 1 -3 1 3 -3 1 -1 -3
-1 3 1 3 1 -1 -3 -3 -1 -1 -3 -3 -3 -1 16 -1 -3 3 -1 -1 -1 -1 1 1 -3
3 1 3 3 1 -1 1 -3 1 -3 1 1 -3 -1 17 1 3 -1 3 3 -1 -3 1 -1 -3 3 3 3
-1 1 1 3 -1 -3 -1 3 -1 -1 -1 18 1 1 1 1 1 -1 3 -1 -3 1 1 3 -3 1 -3
-1 1 1 -3 -3 3 1 1 -3 19 1 3 3 1 -1 -3 3 -1 3 3 3 -3 1 -1 1 -1 -3
-1 1 3 -1 3 -3 -3 20 -1 -3 3 -3 -3 -3 -1 -1 -3 -1 -3 3 1 3 -3 -1 3
-1 1 -1 3 -3 1 -1 21 -3 -3 1 1 -1 1 -1 1 -1 3 1 -3 -1 1 -1 1 -1 -1
3 3 -3 -1 1 -3 22 -3 -1 -3 3 1 -1 -3 -1 -3 -3 3 -3 3 -3 -1 1 3 1 -3
1 3 3 -1 -3 23 -1 -1 -1 -1 3 3 3 1 3 3 -3 1 3 -1 3 -1 3 3 -3 3 1 -1
3 3 24 1 -1 3 3 -1 -3 3 -3 -1 -1 3 -1 3 -1 -1 1 1 1 1 -1 -1 -3 -1 3
25 1 -1 1 -1 3 -1 3 1 1 -1 -1 -3 1 1 -3 1 3 -3 1 1 -3 -3 -1 -1 26
-3 -1 1 3 1 1 -3 -1 -1 -3 3 -3 3 1 -3 3 -3 1 -1 1 -3 1 1 1 27 -1 -3
3 3 1 1 3 -1 -3 -1 -1 -1 3 1 -3 -3 -1 3 -3 -1 -3 -1 -3 -1 28 -1 -3
-1 -1 1 -3 -1 -1 1 -1 -3 1 1 -3 1 -3 -3 3 1 1 -1 3 -1 -1 29 1 1 -1
-1 -3 -1 3 -1 3 -1 1 3 1 -1 3 1 3 -3 -3 1 -1 -1 1 3
Hopping of the reference signal may be applied as described
below.
A sequence group number u of slot n.sub.s may be defined based on a
group hopping pattern f.sub.gh(n.sub.s) and a sequence shift
pattern f.sub.ss by an equation given below.
u=(f.sub.gh(n.sub.s)+f.sub.ss)mod 30 [Equation 6]
17 different group hopping patterns and 30 different sequence shift
patterns may exist. Group hopping may be applied or not applied by
a group-hopping-enabled parameter which is a cell specific
parameter provided by the higher layer. Further, the group hopping
for the PUSCH may not be applied to specific UE by a
disable-sequence-group-hopping parameter which is a UE specific
parameter. The PUCCH and the PUSCH may have the same group hopping
pattern and different sequence shift patterns.
The group hopping pattern f.sub.gh(n.sub.s) is the same with
respect to the PUSCH and the PUCCH and may be defined by an
equation given below.
.function..times..times..times..times..times..times..times..times..times.-
.times..function..times..times..times..times..times..times..times..times..-
times..times..times..times..times..times. ##EQU00002##
In the above equation, c(i) as an imitation pseudo-random sequence
which is a PN sequence may be defined by a gold sequence having a
length of -31. An equation given below shows one example of the
gold sequence c(n). c(n)=(x.sub.1(n+N.sub.c)+x.sub.2(n+N.sub.c))mod
2 x.sub.1(n+31)=(x.sub.1(n+3)+x.sub.1(n))mod 2
x.sub.2(n+31)=(x.sub.2(n+3)+x.sub.2(n+2)+x.sub.1(n+1)+x.sub.1(n))mod
2 [Equation 8]
Herein, Nc=1600, x.sub.1(i) represents a 1 m-th sequence, and
x.sub.2(i) represents a 2 m-th sequence. The imitation
pseudo-number sequence generator may be initialized to
##EQU00003## at the beginning of each radio frame.
Definition of the sequence shift pattern f.sub.ss may be different
with respect to the PUCCH and the PUSCH. The sequence shift pattern
of the PUCCH may be given as f.sub.ss.sup.PUCCH=N.sub.ID.sup.cell
mod 30. The sequence shift pattern of the PUSCH may be given as
f.sub.ss.sup.PUSCH=(f.sub.ss.sup.PUCCH+.DELTA..sub.ss) mod 30 and
.alpha..sub.ss.di-elect cons.{0, 1, . . . , 29} may be configured
by the higher layer.
The sequence hopping may be applied only to a reference signal
sequence having a length longer than 6N.sub.sc.sup.RB. With respect
to a reference signal sequence having a length shorter than
6N.sub.sc.sup.RB, the base sequence number is given as v=0 in the
base sequence group. With respect to the reference signal sequence
having the length longer than 6N.sub.sc.sup.RB, the base sequence
number v in the base sequence group in slot n.sub.s may be defined
by Equation 10.
.function..times..times..times..times..times..times..times..times..times.-
.times..times..times..times..times..times..times..times..times..times..tim-
es. ##EQU00004##
c(i) may be expressed by an example of Equation 8 given above. The
sequence hopping may be applied or not applied by a
sequence-hopping-enabled parameter which is a cell specific
parameter provided by the higher layer. Further, the sequence
hopping for the PUSCH may not be applied to specific UE by the
disable-sequence-group-hopping parameter which is the UE specific
parameter. The imitation pseudo-number sequence generator may be
initialized to
##EQU00005## at the beginning of each radio frame.
A PUSCH DMRS sequence r.sub.PUSCH.sup.(.lamda.)() depending on a
layer .lamda.(0, 1, . . . , .gamma.-1) may be defined by Equation
11.
r.sub.PUSCH.sup.(.lamda.)(mM.sub.sc.sup.RS+n)=w.sup.(.lamda.)(m)r.sub.u,v-
.sup.(.alpha..sup..lamda..sup.)(n) [Equation 10]
In the above equation, m=0, 1, . . . and n=0, . . . ,
M.sub.sc.sup.RS-1. M.sub.sc.sup.RS=M.sub.sc.sup.PUSCH. An
orthogonal sequence w.sup.(.lamda.)(m) may be determined according
to a table to be described below.
In the slot n.sub.s, the cyclic shift may be given as
.alpha.=2.pi.n.sub.cs/12 and n.sub.cs may be defined by an equation
given below.
n.sub.cs,.lamda.=(n.sub.DMRS.sup.(1)+n.sub.DMRS,.lamda..sup.(2)+n.-
sub.PN(n.sub.s))mod 12 [Equation 11]
In the above equation, n.sup.(1).sub.DMRS may be determined
according to a cyclicShift parameter provided by the higher layer.
A table given below shows an example of n.sup.(1).sub.DMRS
determined according to the cyclicShift parameter.
TABLE-US-00004 TABLE 4 Parameter n.sup.(1).sub.DMRS 0 0 1 2 2 3 3 4
4 6 5 8 6 9 7 10
Referring back to the above equation, n.sup.(2).sub.DMRS,.lamda.
may be determined by a DMRS cyclic shift field in DCI format 0 for
the transport block depending on corresponding PUSCH transmission.
A table given below shows an example of n.sup.(2).sub.DMRS,.lamda.
determined according to DMRS cyclic shift field.
TABLE-US-00005 TABLE 5 DMRS cyclic n.sup.(2).sub.DMRS, .lamda.
[w.sup.(.lamda.)(0) w.sup.(.lamda.)(1)] shift field .lamda. = 0
.lamda. = 1 .lamda. = 2 .lamda. = 3 .lamda. = 0 .lamda. = 1 .lamda.
= 2 .lamda. = 3 000 0 6 3 9 [1 1] [1 1] [1 -1] [1 -1] 001 6 0 9 3
[1 -1] [1 -1] [1 1] [1 1] 010 3 9 6 0 [1 -1] [1 -1] [1 1] [1 1] 011
4 10 7 1 [1 1] [1 1] [1 1] [1 1] 100 2 8 5 11 [1 1] [1 1] [1 1] [1
1] 101 8 2 11 5 [1 -1] [1 -1] [1 -1] [1 -1] 110 10 4 1 7 [1 -1] [1
-1] [1 -1] [1 -1] 111 9 3 0 6 [1 1] [1 1] [1 -1] [1 -1]
n.sub.PN(n.sub.s) may be defined by an equation given below.
n.sub.PN(n.sub.s)=.SIGMA..sub.i=0.sup.7c(8N.sub.symb.sup.ULn.sub.s+i)2.su-
p.i [Equation 12]
c(i) may be expressed by the example of Equation 8 given above and
applied for each cell of c(i). The imitation pseudo-number sequence
generator may be initialized to
##EQU00006## at the beginning of each radio frame.
The vector of the reference signal may be precoded by an equation
given below.
.function..upsilon..times..times. ##EQU00007##
In the above equation, P represents the number of antenna ports
used for the PUSCH transmission. W represents a precoding matrix.
With respect to the PUSCH transmission using the single antenna
port, P=1, W=1, and .gamma.=1. Further, with respect to spatial
multiplexing, P=2 or 4.
With respect to each antenna port used for the PUSCH transmission,
the DMRS sequence is multiplied by an amplitude scaling factor
.beta..sub.PUSCH and sequentially mapped to the resource block. A
set of physical resource blocks used for the mapping is the same as
the set of physical resource blocks used for the PUSCH
transmission. In the subframe, the DMRS sequence may be first
mapped to the resource element in a direction in which the DMRS
sequence increases in the frequency domain and thereafter, in a
direction in which the slot number increases. The DMRS sequence may
be mapped to a fourth SC-FDMA symbol (SC-FDMA symbol 3) in the case
of the normal CP and a third SC-FDMA symbol (SC-FDMA symbol 2) in
the case of the extension CP.
FIGS. 7a and 7b are One Example of a Subframe in which a DMRS for a
PUSCH is Transmitted.
The structure of the subframe in FIG. 7a shows a case of the normal
CP. The subframe includes the first slot and the second slot. Each
of the first slot and the second slot includes 7 SC-FDMA symbols.
Symbol indexes of 0 to 13 are granted to 14 SC-FDMA symbols in the
subframe. The reference signal may be transmitted through the
SC-FDMA symbols having symbol indexes 3 and 10. The reference
signal may be transmitted by using the sequence. The Zadoff-Chu
(ZC) sequence may be used as the reference signal sequence and
various ZC sequences may be generated according to a root index and
a cyclic shift value. The base station allocates different cyclic
shift values to the terminal to estimate channels of a plurality of
terminals through an orthogonal sequence or quasi-orthogonal
sequence. Locations of the frequency domains occupied by the
reference signal in may be the same as each other or different from
each other in two slots in the subframe. In two slots, the same
reference signal sequence is used. Data may be transmitted through
the residual SC-FDMA symbols other than the SC-FDMA symbol in which
the reference signal is transmitted.
The structure of the subframe in FIG. 7b shows a case of the
extension CP. The subframe includes the first slot and the second
slot. Each of the first slot and the second slot includes 6 SC-FDMA
symbols. Symbol indexes of 0 to 11 are granted to 12 SC-FDMA
symbols in the subframe. The reference signal is transmitted
through the SC-FDMA symbols having symbol indexes 2 and 8. The data
is transmitted through the residual SC-FDMA symbols other than the
SC-FDMA symbol in which the reference signal is transmitted.
<Carrier Aggregation>
Hereinafter, a carrier aggregation (CA) system will be
described.
The carrier aggregation (CA) system means aggregating multiple
component carriers (CCs). By the carrier aggregation, the existing
meaning of the cell is changed. According to the carrier
aggregation, the cell may mean a combination of a downlink
component carrier and an uplink component carrier or a single
downlink component carrier.
Further, in the carrier aggregation, the cell may be divided into a
primary cell, secondary cell, and a serving cell. The primary cell
means a cell that operates at a primary frequency and means a cell
in which the UE performs an initial connection establishment
procedure or a connection reestablishment procedure with the base
station or a cell indicated by the primary cell during a handover
procedure. The secondary cell means a cell that operates at a
secondary frequency and once an RRC connection is established, the
secondary cell is configured and is used to provide an additional
radio resource.
As described above, the carrier aggregation system may support a
plurality of component carriers (CC), that is, a plurality of
serving cells unlike a single carrier system.
The carrier aggregation system may support cross-carrier
scheduling. The cross-carrier scheduling is a scheduling method
that may perform resource allocation of the PDSCH transmitted
through another component carrier through the PDCCH transmitted
through a specific component carrier and/or resource allocation of
the PUSCH transmitted through other component carrier other than
the component carrier fundamentally linked with the specific
component carrier.
<Introduction of Small Cell>
Meanwhile, in a next-generation mobile communication system, it is
anticipated that a small cell having a small cell coverage radius
will be added into coverage of the existing cell and it is
anticipated that the small cell will process more traffic. Since
the existing cell has larger than the small cell, the existing call
may be called a macro cell. Hereinafter, it will be described with
reference to FIG. 10.
FIG. 8 is a Diagram Illustrating an Environment of Heterogeneous
Networks of a Macro Cell and a Small Cell which May Become a
Next-Generation Wireless Communication System.
Referring to FIG. 8, a heterogeneous-network environment is shown,
in which a macro cell by the existing base station 200 overlaps
with a small cell by one or more small base stations 300a, 300b,
300c, and 300d. Since the existing base station provides the larger
coverage than the small base station, the existing base station may
be called a macro base station (macro eNodeB, or MeNB). In the
present specification, terms such as the macro cell and the macro
base station will be mixedly used. The UE that accesses the macro
cell 200 may be referred to as macro UE. The macro UE receives a
downlink signal from the macro base station and transmits an uplink
signal to the macro base station.
In the heterogeneous networks, the macro cell is configured as a
primary cell (Pcell) and the small cell is configured as a
secondary cell (Scell) to fill a coverage gap of the macro cell.
Further, the small cell is configured as the primary cell (Pcell)
and the macro cell is configured as the secondary cell (Scell) to
boost overall performance.
Meanwhile, the small cell may use a frequency band assigned to
current LTE/LTE-A or use a higher frequency band (e.g., a band of
3.5 GHz or higher).
On the other hand, in a next LTE-A system, it is considered that
the small cell may not be independently used and the small cell may
be used only as a macro-assisted small cell which may be used under
assistance of the macro cell.
The small cells 300a, 300b, 300c, and 300d may have similar channel
environments to each other and since the small cells 300a, 300b,
300c, and 300d are positioned at distances which are proximate to
each other, interference among the small cells may be a large
issue.
In order to reduce an interference influence, the small cells 300b
and 300c may extend or reduce coverage thereof. The extension and
reduction of the coverage is referred to as cell breathing. For
example, as illustrated in FIG. 9, the small cells 300b and 300c
may be turned on or off according to a situation.
On the other hand, the small cell may use the frequency band
assigned to the current LTE/LTE-A or use the higher frequency band
(e.g., the band of 3.5 GHz or higher).
<Machine Type Communication (MTC)>
Meanwhile, hereinafter, the MTC will be described.
FIG. 9 Illustrates One Example of Machine Type Communication
(MTC).
The machine type communication (MTC) represents information
exchange through between MTC devices 100 through a base station 200
or information exchange between the MTC device 100 and an MTC
server 700 through the base station, which does not accompany human
interaction.
The MTC server 700 is an entity which communicates with the MTC
device 100. The MTC server 700 executes an MTC application and
provides an MTC specific service to the MTC device.
The MTC device 100 as a wireless device providing the MTC may be
fixed or mobile.
The service provided through the MTC has discrimination from a
service in communication in which human intervenes in the related
art and includes various categories of services including tracking,
metering, payment, a medical field service, remote control, and the
like. In more detail, the service provided through the MTC may
include electric meter reading, water level measurement,
utilization of a monitoring camera, reporting of an inventory of a
vending machine, and the like.
As peculiarities of the MTC device, since a transmission data
amount is small and uplink/downlink data transmission/reception
often occurs, it is efficient to decrease manufacturing cost of the
MTC device and reduce battery consumption according to the low data
transmission rate. The MTC device is characterized in that mobility
is small, and as a result, the MTC device is characterized in that
a channel environment is not almost changed.
Meanwhile, the MTC is also called Internet of Things (IoT).
Accordingly, the MTC device may be called an IoT device.
FIGS. 10a and 10b are Exemplary Diagrams Illustrating not the
Entirety of an Uplink System Band but a Partial Subband of the MTC
Device.
As one method for low cost of the MTC device, the MTC device may
use a subband at, for example, approximately 1.4 MHz regardless of
an uplink system bandwidth of the cell as illustrated in FIG.
10a.
In this case, a region of the subband in which the MTC device
operates may be positioned at a central area (for example, 6
central PRBs) of the uplink system bandwidth of the cell as
illustrated in FIG. 9a.
Alternatively, as illustrated in FIG. 10b, multiple subbands of the
MTC device are provided in one subframe for multiplexing of the MTC
devices in the subframe, and as a result, the MTC devices may have
different subbands. In this case, a majority of MTC devices may
have other subbands other than the central area (for example, 6
central PRBs) of the system band of the cell.
FIG. 11a is an Example of Cell Coverage Enhancement for an MTC
Device.
In recent years, it is considered that cell coverage enhancement or
coverage enhancement (CE) of the base station extends for the MTC
device 100 and various techniques for the cell coverage enhancement
are discussed.
However, in the case where the coverage of the cell extends, when
the MTC device positioned in the coverage enhancement transmits an
uplink channel, the base station undergoes a difficulty in
receiving the uplink channel.
FIG. 11b is an Exemplary Diagram Illustrating an Example of
Transmitting a Bundle of Uplink Channels.
As known with reference to FIG. 11b, the MTC device positioned in
the coverage enhancement area repeatedly transmits the uplink
channel (for example, the PUCCH and/or PUSCH) on multiple subframes
(for example, N subframes). As described above, the uplink channels
which are repeated on the multiple subframes are called a bundle of
the uplink channels.
Meanwhile, the base station receives the bundle of the uplink
channels on the multiple subframes and decodes a part or the
entirety of the bundle to increase decoding success rate.
Meanwhile, since the MTC device may exist at a location where the
signal is weak, performance may deteriorate when the base station
estimates the channel by using the DMRS transmitted by the MTC
device.
In order to solve the performance deterioration, it may be
considered that the MTC device repeatedly transmits the DMRS.
However, since a channel situation has characteristics that the
channel situation may vary with time, there may be a limit in
improving channel estimation performance of the base station only
by repeatedly transmitting the DMRS by the MTC device.
<Disclosure of Present Specification>
Therefore, the disclosure of the present specification has been
made in an effort to present a method that solves the problem.
In detail, one disclosure of the present specification suggests
increasing the density (by the unit of single or multiple
slots/subframes/radio frames) of the reference signal for the
uplink channel. In more detail, one disclosure of the present
specification proposes a method for increasing the density of the
DMRS for demodulating the PUSCH. In addition, one disclosure of the
present specification suggests a method that handles issues (e.g.,
SRS collisions, etc.) which may occur as the density of the DMRS
increases.
Hereinafter, the method is described based on transmission of the
PUSCH, but the corresponding description may be applied even to
another channel (including even the downlink channel).
I. Method for Enhancing Reference Signal for Demodulating PUSCH
In the existing LTE Rel-11 system, the DMRS for demodulating the
PUSCH is mapped to OFDMA (SC-FDMA) symbol #3 and OFDMA (SC-FDMA)
symbol #10 based on the normal CP and mapped to OFDMA (SC-FDMA)
symbol #2 and OFDMA (SC-FDMA) symbol #8 based on the extended CP.
As one method for increasing the density of the reference signal
for demodulating the PUSCH, it may be considered that the existing
DMRS is reused and an additional reference signal (hereinafter,
referred to as to `extended DMRS`).
FIG. 12 is an Exemplary Diagram Illustrating a Method for Enhancing
a DMRS for Demodulating a PUSCH.
Referring to FIG. 12, one subframe is illustrated based on the
normal CP. The existing DMRS is transmitted in symbol #3 and symbol
#10. In order to increase the density, for example, an additional
reference signal (extended DMRS) may be transmitted on symbol #0
and symbol #7.
The PUSCH may include uplink control information (UCI). The UCI may
include the HARQ-ACK/NACK and the RI as described above. The UCI
including the HARQ-ACK/NACK may be transmitted through OFDM
(SC-FDMA) symbols #2, #4, #9, and #11 based on the normal CP and
the UCI including the RI may be transmitted through OFDM (SC-FDMA)
symbols #1, #5, #8, and #12. Therefore, transmitting the additional
reference signal may be excluded from a location where the HARQ-ACK
or the RI may be transmitted. In this case, even though the density
of the reference signal for demodulating the PUSCH is increased, it
is advantageous in that UCI mapping need not be modified. However,
since the MTC device may not transmit the RI, it may be considered
that the additional reference signal is mapped to the OFDM
(SC-FDMA) symbol to which the RI may be mapped.
The OFDM (SC-FDMA) symbol in which the additional reference signal
(that is, extended DMRS) may be transmitted is illustrated below
according to each CP type. Normal CP: #0, (#1), (#5), #6, #7, (#8),
(#12), #13 Extended CP: (#0), (#4), #5, (#6), (#10), #11
OFDM (SC-FDMA) symbol indexes in parentheses indicate the symbols
to which the RI may be mapped. The additional reference signal
(that is, enhanced DRMS) may be mapped only in a subset of the OFDM
(SC-FDMA) symbol indexes. Meanwhile, in a last OFDM (SC-FDMA)
symbol, the SRS may be transmitted and when the SRS is transmitted,
it may be considered that the last OFDM (SC-FDMA) symbol is
excluded from a region where the additional reference signal (that
is, extended DMRS) may be transmitted by the unit of the subframe
or the slot in order to prevent the density of the reference signal
for demodulating the PUSCH from being changed. As one example, the
additional reference signal (that is, enhanced DRMS) may be
transmitted in OFDM (SC-FDMA) symbols #0 and #7 based on the normal
CP.
When the last OFDM (SC-FDMA) symbol (#6 and/or #13 based on the
normal CP) is included in the region to which the additional
reference signal (that is, extended DMRS) is mapped by the unit of
the subframe or the slot, a situation in which the SRS and the
additional reference signal (that is, extended DMRS) overlap with
the same symbol may be processed as described in Section III given
below.
On the other hand, a cyclic shift and an orthogonal cover code
(OCC) may be applied to the DMRS for demodulating the PUSCH in the
related art and a combination of the corresponding cyclic shift and
the OCC varies for each UE to permit a plurality of PUSCHs to be
multiplexed even with respect to the same time/frequency resource.
As one example, when a first UE applies OCC [1 1] to the DMRS for
the PUSCH transmitted thereby and a second UE applies OCC [1 -1] to
the DMRS for the PUSCH transmitted thereby, the base station may
divide the DMRSs of the respective PUSCHs and detect the UL-SCH
(including the UCI) included in each PUSCH again from the
corresponding divided DMRSs (even in a situation in which RBs in
which both PUSCHs are transmitted partially overlap with each
other).
In a next system, even when the additional reference signal (that
is, extended DMRS) is introduced as described in this section,
multiplexing the plurality of PUSCHs may be considered and the OCC
needs to be designed for this case. Hereinafter, a more detailed
example of an OCC design method will be described. Next, the
existing DMRS for the PUSCH as the DMRS included in the existing
Rel-11 means the DMRSs mapped to OFDMA (SC-FDMA) symbol #3 and
OFDMA (SC-FDMA) symbol #10 based on the normal CP.
As a first exemplary method, the cyclic shift and the OCC are
applied to the existing DMRS for the PUSCH similarly to the method
used in the existing Rel-11 PUSCH. That is, the OCC having a length
of 2 is applied to the existing DMRS. The cyclic shift and/or the
OCC may be independently applied to the additional reference signal
(that is, extended DMRS). The base station may separately add a
field associated with the cyclic shift for the additional reference
signal (that is, extended DMRS) into the DCI transmitted to the MTC
device. Alternatively, the base station includes only a field
associated with the cyclic shift for the existing DMRS in the DCI
transmitted to the MTC device and the field may be used for both
the existing DMRS and the additional reference signal. For example,
the same cyclic shift and OCC may be applied to the existing DMRS
and the additional reference signal according to the field.
Alternatively, a value of a table indicated by the field associated
with the cyclic shift may be extended to include information on the
additional reference signal 9 that is, extended DMRS). In this
method, the PUSCH which is enabled to be demodulated according to
the existing DMRS and the PUSCH which is enabled to be demodulated
according to the additional reference signal (that is, extended
DMRS) may be permitted to be multiplexed and in this case, the
additional reference signal (that is, extended DMRS) may not be
used due to an influence of interference.
As a second exemplary method, the cyclic shift and/or the OCC may
be configured by considering both the existing DRMS and the
additional reference signal (that is, enhanced DRMS). When the
number of OFDM (SC-FDMA) symbols to which the additional reference
signal (that is, extended DMRS) is mapped is M, it may be
considered that the OCC having a length of M+2 is applied. In this
method, the PUSCHs demodulated according to the additional
reference signal (that is, extended DMRS) may be permitted to be
multiplexed with each other. As one example, in the case of M=2,
the OCC may be configured by [+1 +1 +1 +1], [+1 +1 -1 -1], [+1 -1
+1 -1], and [+1 -1 -1 +1] or a combination of a form in which all
codes are changed with respect to [+1 +1 +1 +1], [+1 +1 -1 -1], [+1
-1 +1 -1], and [+1 -1 -1 +1].
When PUSCH mapping is not performed with respect to some OFDM
(SC-FDMA) symbols and when the DMRS is transmitted in the
corresponding OFDM (SC-FDMA) symbol, an OCC application method may
be different from that when the PUSCH is mapped in all OFDM
(SC-FDMA) symbols. As one example, the length of the OCC and a
sequence type may be differently applied.
As one example, the OCC having a length of 3 is applied to the
additional reference signal (that is, extended DMRS) and when the
DMRS includes the last OFDM (SC-FDMA) symbol, the DMRS mapped to
the last OFDM (SC-FDMA) symbol is not also transmitted in a
subframe in which a cell-specific SRS is enabled to be transmitted
and a form in which the length of the OCC for the additional
reference signal (that is, extended DMRS) is reduced to 2 (=3-1)
may be applied.
II. Method for Newly Designing Structure of Reference Signal for
Demodulating PUSCH
As another method for increasing the density of the reference
signal for demodulating the PUSCH, designing a mapping structure of
the reference signal again from the beginning may be considered. In
this case, the location of the DMRS may be designed to be evenly
distributed according to the number of DMRSs to be introduced (by
the unit of single or multiple slots/subframes/radio frames).
FIG. 13 Illustrates an Example in which a New DMRS for Demodulating
the PUSCH is Mapped.
As known with reference to FIG. 13, as another method for
increasing the density of the reference signal for demodulating the
PUSCH, the new DMRS may be mapped to, for example, the subset of
#1, #5, #8, and #12 in the subframe of the normal CP.
Next, a detailed example of a method that may newly map the DMRS by
increasing the density is described.
1) Normal CP:
Case 1-1: As illustrated in FIG. 13, the reference signal for
demodulating the PUSCH is mapped to the subset of OFDM (SC-FDMA)
symbols #1, #5, #8, and #12.
Case 1-2: The reference signal for demodulating the PUSCH is mapped
to the subset of OFDM (SC-FDMA) symbols #2, #3, #4, #9, #10, and
#11.
2) Extended CP:
Case 2-1: The reference signal for demodulating the PUSCH is mapped
to the subset of OFDM (SC-FDMA) symbols #2, #3, #8, and #9.
According to the method described in this section, a method in
which the UCI is mapped in a case where the UCI is transmitted
through the PUSCH needs to be redefined. The case where the UCI is
transmitted through the PUSCH may include a case where the MTC
device transmits an aperiodic CSI and a case where a periodic CSI
and/or HARQ-ACK to be transmitted to the PUCCH piggybacks to the
PUSCH. Herein, the latter case may be interpreted as a situation in
which only the PUSCH may be transmitted when the PUCCH and the
PUSCH collide with each other.
Since the HARQ-ACK and the RI primarily have a higher priority than
another UCI, the HARQ-ACK and the RI may be transmitted while being
mapped to the OFDM (SC-FDMA) symbol approximate to the OFDM
(SC-FDMA) symbol to which the DMRS is mapped. Further, since the
SRS may be transmitted in the case of the last OFDM (SC-FDMA)
symbol, it may be considered that the HARQ-ACK and/or the RI are/is
mapped to the last OFDM (SC-FDMA) symbol (by the unit of the
subframe/slot) due to the collision issue with the SRS. Since the
MTC device may not transmit the RI, a mapping method for the
HARQ-ACK is described in an example given below. Next, one example
of a region to which the HARQ-ACK may be mapped for each case is
described. In Case 1-1, the HARQ-ACK is mapped to all or the subset
of OFDM (SC-FDMA) symbols #2, #3, #4, #9, #10, and #11. In more
detail, the HARQ-ACK may be mapped to OFDM (SC-FDMA) symbols #2,
#4, #9, and #11. In Case 1-2, the HARQ-ACK may be mapped to all or
the subset of OFDM (SC-FDMA) symbols #1, #5, #8, and #12. In Case
2-1, the HARQ-ACK may be mapped to all or the subset of OFDM
(SC-FDMA) symbols #1, #4, #7, and #10.
The OCC may be applied even to a new reference signal (that is,
DMRS) for demodulating the PUSCH having a new structure and new
various PUSCHs demodulated according to the new reference signal
may be multiplexed based on the applied OCC. When the number of
DMRSs per subframe in the PUSCH having the new structure is M, as
the OCC, (1) it may be considered that the OCC having a length of M
is applied or (2) it may be considered that M/2 OCC combinations
having a length of 2 are applied. (3) Alternatively, it may be
considered that two OCC combinations having a length of M/2 are
applied by the unit of the slot. When the PUSCH mapping is not
performed with respect to some OFDM (SC-FDMA) symbols and when the
DMRS is transmitted in the corresponding OFDM (SC-FDMA) symbol, the
OCC application method may be different from that when the PUSCH is
mapped in all OFDM (SC-FDMA) symbols. As one example, the length of
the OCC and the sequence type may be differently applied.
Meanwhile, the additional reference signal (that is, extended DMRS)
is mapped to the last OFDM (SC-FDMA) symbol (#6 and/or #13 based on
the normal CP), and as a result, it may be considered that the
situation in which the extended DMRS overlaps with the SRS is
processed by a method of Section III given below.
III. UE Operation when SRS and PUSCH DRMS Collide with Each
Other
In a situation in which the PUSCH is demodulated according to the
additional reference signal (that is, enhanced DRMS), when the
additional reference signal (that is, enhanced DRMS) is transmitted
in the last OFDM (SC-FDMA) symbol or when the additional reference
signal is transmitted in the OFDM (SC-FDMA) symbol in which the SRS
may be transmitted, the additional reference signal may collide
with the SRS which may be transmitted in the last OFDM (SC-FDMA)
symbol or the OFDM (SC-FDMA) symbol in which the SRS may be
transmitted by the unit of the subframe.
FIG. 14 Illustrates an Example in which the New DMRS for
Demodulating the PUSCH Collides with the SRS.
Referring to FIG. 14, when the additional reference signal (that
is, enhanced DRMS) is transmitted in the last OFDM (SC-FDMA)
symbol, the additional reference signal may collide with the
SRS.
Therefore, in the case of the collision, the operations need to be
designated.
The operation described in this section may be applied even to the
SRS is used as the demodulation reference signal for the PUSCH in
addition to the collision. That is, a situation in which the
subframe in which the SRS is transmitted and the subframe in which
the SRS is not transmitted have different densities of the
demodulation reference signal may be considered.
Next, in the existing Rel-11 operation, conditions in which the
PUSCH is not used in the last OFDM (SC-FDMA) symbol (by the unit of
the subframe) are listed.
TABLE-US-00006 TABLE 6 Condition 1: not a part of the last SC-FDMA
symbol on the same subframe when the UE transmits the SRS in the
subframe Condition 2: not a part of the last SC-FDMA symbol on the
subframe in which a cell-specific SRS is configured when PUSCH
transmission generally or partially overlaps with a cell-specific
SRS bandwidth Condition 3: not a part of the SC-FDMA symbol
reserved for SRS transmission available in the subframe in which a
UE-specific aperiodic SRS is transmitted Condition 4: not a part of
the SC-FDMA reserved for SRS transmission available in a
UE-specific periodic SRS subframe when the UE configures multiple
timing advance groups (TAGs)
III-1. Method for Determining Configuration Information for SRS
Transmitted by MTC Device
As described above, the MTC device may transmit/receive a data
channel/control channel by using only a reduced bandwidth (that is,
an MTC subband) smaller than an entire system of the cell as
described with reference to FIGS. 10a and 10b.
However, the MTC device may influence the SRS transmitted by the
legacy UE in transmitting the uplink channel (for example, PUSCH or
PUCCH).
FIG. 15 Illustrates an Example in which an Uplink Channel
Transmitted by the MTC Device Influences the SRS Transmitted by the
Legacy UE.
As known with reference to FIG. 15, the uplink channel transmitted
by the MTC device, for example, the PUCCH/PUSCH may influence the
SRS transmitted by the legacy UE.
Therefore, hereinafter, this will be described.
In order to consider an issue in which uplink transmission of the
MTC device collides with the SRS of the legacy UE, it may be
primarily considered that all or some of the SRS configuration
information for the SRS of the legacy UE is transferred to the MTC
device through a higher layer signal. In more detail, the SRS
configuration information may include information on the
cell-specific SRS subframe and/or cell-specific SRS bandwidth. The
MTC device may (additionally) apply Condition 2 even to the SRS
configuration information for the SRS of the legacy UE based on the
information. That is, when the PUSCH transmission of the MTC device
overlaps with all or some of the SRS bandwidth depending on the SRS
configuration information for the SRS of the legacy UE and when the
subframe in which the MTC device will transmit the PUSCH is a
subframe in which the cell-specific SRS depending on the SRS
configuration information for the SRS of the legacy UE is
configured, the MTC device may not transmit the PUSCH on the last
SC-FDMA symbol. In order to prevent the PUSCH from being
transmitted on the last symbol as described above, the MTC device
may rate-match the PUSCH only with other symbols other than the
last symbol.
FIG. 16 is an Exemplary Diagram Illustrating One Method for
Preventing the SRS Transmitted by the Legacy UE and the PUSCH
Transmitted by the MTC Device from Colliding with Each Other.
The base station transmits the SRS configuration information for
the legacy UE in the cell to the legacy UE, but transmits the SRS
configuration information even to the MTC device. The SRS
configuration information may include information (that is,
SRS-SubframeConfig) on the subframe in which the SRS may be
transmitted and information (SRS-BandwidthConfig) on a bandwidth in
which the SRS may be transmitted.
When the PUSCH transmission of the MTC device overlaps with all or
some of the SRS bandwidth depending on the SRS configuration
information for the SRS of the legacy UE and when the subframe in
which the MTC device will transmit the PUSCH is a subframe in which
the cell-specific SRS depending on the SRS configuration
information for the SRS of the legacy UE is configured, the MTC
device may use the reduced PUSCH format. That is, the MTC device
may not transmit the PUSCH on the last SC-FDMA symbol of the
corresponding subframe. In order to prevent the PUSCH from being
transmitted on the last symbol as described above, the MTC device
may rate-match the PUSCH only with other symbols other than the
last symbol.
Further, the MTC device may drop transmission of the SRS on the
last symbol in the subframe indicated by the subframe information
in the SRS configuration information for the legacy UE.
Meanwhile, when the legacy UE transmits both the PUCCH including
the HARQ-ACK/NACK and the SRS on the same subframe, the PUCCH and
the SRS may collide with each other. In order to solve the
collision, the shorted PUCCH format is used in the related art.
Herein, the reduced PUCCH means that the sounding reference signal
(SRS) is transmitted instead of the PUCCH in the last symbol.
Therefore, when the reduced PUCCH format is configured (when
simultaneous transmission of the SRS and the HARQ-ACK is
configured), the MTC device may determine whether to apply the
reduced PUCCH format by considering the cell-specific SRS subframe
and/or cell-specific SRS bandwidth for the SRS of the legacy UE.
For example, after the MTC device receives both the SRS
configuration information for the legacy UE and the SRS
configuration information for the MTC device itself, when one of
both SRS configuration information satisfies the condition (in
particular, when Condition 2 is satisfied), the last OFDM (SC-FDMA)
symbol may be excluded in mapping the PUCCH to be transmitted.
The reduced PUCCH format may be applied when a specific higher
layer signal is turned on. Herein, the specific higher layer signal
may be ackNackSRS-SimultaneousTransmission of the SRS configuration
information for the legacy UE. Alternatively, the reduced PUCCH
format may be applied according to a separate higher layer signal.
The separate higher layer signal may be used for the MTC
device.
The aforementioned contents are described below in brief once more
with reference to drawings.
FIG. 17 is an Exemplary Diagram Illustrating One Method for
Preventing the SRS Transmitted by the Legacy UE and the PUCCH
Transmitted by the MTC Device from Colliding with Each Other.
The base station transmits the SRS configuration information for
the legacy UE in the cell to the legacy UE, but transmits the SRS
configuration information even to the MTC device. The SRS
configuration information may include the information (that is,
SRS-SubframeConfig) on the subframe in which the SRS may be
transmitted and configuration information (that is,
ackNackSRS-Simultaneous Transmission) on for simultaneous
transmission of the SRS and the HARQ-ACK/NACK.
Then, when the simultaneous transmission of the SRS and the
HARQ-ACK/NAC is configured on the subframe indicated by the
subframe information in the SRS configuration information for the
legacy UE, the MTC device may transmit the PUCCH only on the
symbols other than the last symbol on the subframe according to the
reduced PUCCH format.
In this case, even though the SRS is not actually transmitted on
the last symbol in the subframe indicated by the subframe
information, the reduced PUCCH format may be used.
Meanwhile, the MTC device may drop the transmission of the SRS on
the last symbol in the subframe indicated by the subframe
information in the SRS configuration information for the legacy
UE.
Meanwhile, a more detailed example is described below. When a PUCCH
transmission region of the MTC device wholly or partially overlaps
with the cell-specific SRS bandwidth of the legacy UE, (1) the
reduced PUCCH format may be continuously used or (2) whether the
reduced PUCCH format is used may be determined according to the
higher layer signal for the MTC device. When the PUCCH transmission
region of the MTC device does not overlap with the cell-specific
SRS bandwidth of the legacy UE, the MTC device may determine
whether the reduced PUCCH format is used according to the higher
layer signal indicating whether the HARQ-ACK and the SRS of the
legacy UE are simultaneously transmitted. Code division
multiplexing (CDM) is enabled between the PUCCH of the legacy UE
and the PUCCH of the MTC device through the method and the SRS of
the legacy UE may be continuously protected so that the MTC device
uses the reduced PUCCH format in a frequency domain in which the
SRS of the legacy UE may be transmitted.
As another method, when not the entirety of the system band of the
cell but the MTC subband (e.g., 6 RBs) is allocated to the MTC
device, the base station may transfer information on a subframe
which should not be mapped to the last OFDM (SC-FDMA) symbol to the
MTC device through the higher layer signal. Similarly, as a
verification result according to the subframe information, when the
reduced PUCCH format is configured on the corresponding subframe
(when the simultaneous transmission of the SRS and the HARQ-ACK is
configured), the MTC device may apply the reduced PUCCH format in
the corresponding subframe.
Meanwhile, the base station may consider that the (cell-specific)
configuration information (e.g., the SRS bandwidth and the SRS
subframe) for the SRS of the MTC device coincides with the
information on the configuration of the SRS of the legacy UE. In
this case, the base station may transfer only the configuration
information on the SRS of the MTC device without the need for
separately transferring the configuration information for the SRS
for the legacy UE to the MTC device. Nevertheless, the MTC device
may prevent the SRS of the MTC device and the PUCCH/PUSCH of the
legacy UE from colliding with each other through the method.
However, since the commonly configured (cell-specific) SRS
configuration may enable the SRS of the MTC device and the SRS of
the legacy UE from being multiplexed with each other, when the
quantity of resources occupied between information on actual
transmission SRS transmission and the cell-specific SRS
configuration is large like the U-specific SRS configuration, etc.,
both the legacy UE and the MTC device may unnecessarily perform
rate-matching for the PUCCH/PUSCH or use the reduced PUCCH format
in order to avoid the SRS collision.
III-1-1. SRS Transmission Method of MTC Device
In the case where the (cell-specific) configuration information
(the SRS bandwidth and the SRS subframe) for the SRS of the MTC
device is the same as the configuration information for the SRS of
the legacy UE or the case where the (cell-specific) configuration
information is configured as the subset of the configuration
information for the SRS of the legacy UE, the resource for the SRS
of the MTC device and the resource of the SRS of the legacy UE need
to be separated/distinguished on the corresponding common resource.
In brief, the resource for the SRS of the MTC device and the
resource for the SRS for the legacy UE may be subjected to time
division multiplexing (TDM) and/or frequency division multiplexing
(FDM) and/or code division multiplexing (CDM) through a combination
of a configuration for the UE-specific SRS subframe, a
configuration for the UE-specific SRS bandwidth, a Comb index, and
the like. In more detail, when the SRS of the MTC device and the
SRS of the legacy UE are divided by the TDM and/or FDM, the SRS of
the MTC device may be made to be transmitted by the unit of 6 RBs.
In more detail, 6 RBs for the SRS transmission of the MTC device
may correspond to a specific MTC subband. When the configuration
for the SRS of the MTC device is determined based on the
configuration for the SRS of the legacy UE, the MTC device may not
enable the SRS to be transmitted throughout the entire MTC subband
thereof. As one example, it is assumed that the MTC subband
includes 6 RBs and the MTC device transmits only the PUSCH in the
corresponding MTC subband. In this case, when the base station
determines the configuration of the SRS of the MTC device based on
the configuration for the SRS of the legacy UE, the bandwidth for
the SRS of the MTC device may be determined as the unit of a
minimum of 4 RBs. Further, four RBs may not be positioned on the
MTC subband. In this case, since the MTC device needs to secure a
time required for retuning an RF unit, transmission of the
PUSCH/PUCCH may be limited on some symbols and in this case, the
SRS may not also be transmitted. The method may operate differently
according to the periodic SRS or the aperiodic SRS and as one
example, when boundaries of the SRS to be transmitted when the band
for transmitting the PUSCH and the SRS and the MTC subband do not
overlap with each other corresponds to the periodic SRS, the
transmission of the corresponding SRS may be dropped and when the
SRS to be transmitted is the aperiodic SRS, the PUSCH may be
punctured or the transmission of the PUSCH may be restricted on the
overlapped symbol.
Meanwhile, the MTC device may consider that the SRS is transmitted
throughout the entire MTC subband (e.g., 6 RBs) or limit a
transmission unit to 1 RB or a specific RB (dynamically designated
by the network) in order to drive transmission power to a specific
RE/RB. Alternatively, the MTC device may use only a configuration
based on 6 RBs or less (e.g., 4 RBs) among the configurations for
the SRS of the legacy UE. When the coverage is extended or the SRS
is repeatedly transmitted, the MTC device may transmit the SRS on
multiple consecutive SC-FDMA symbols throughout one or multiple
subframes. As one example, the MTC device may repeatedly transmit
the SRS in all symbols corresponding to the resources for the SRS
transmission. In this case, when the base station transfers the
configuration information for the SRS for the legacy UE (through
the higher layer signal, etc.,), the MTC device may not repeatedly
transmit the SRS of the MTC device on the subframe indicated in the
configuration information. Alternatively, in order to prevent the
collision with the SRS of the legacy UE at the corresponding time,
the MTC device may repeatedly transmit the SRS of the MTC device
only on residual symbols other than the last symbol. As another
method, the MTC device permits the SRS to be transmitted even on
the last SC-FDMA symbol and may transmit the SRS throughout
multiple subframes. The number of repetition times/a repetition
level of the SRS may be determined by the number of symbols in
which the SRS is transmitted. For the repeated transmission of the
SRS, the base station may configure a substrate in which the MTC
device will start the repeated transmission of the SRS in the MTC
device through the higher layer signal. The configuration may be
independently achieved for each coverage enhancement (CE) level or
for each group of the coverage enhancement (CE) level.
Meanwhile, the base station may dynamically configure whether the
MTC device needs to transmit the SRS. As one example, the base
station may indicate a mode to prevent the MTC device from
transmitting the SRS in some bands or a mode to prevent the MTC
device from transmitting the SRS on some subframes in transferring
the SRS configuration for the MTC device. Alternatively, the base
station may indicate whether the MTC device transmits the SRS
through the higher layer signal. The base station may designate
whether the MTC device transmits the SRS through the higher layer
signal differently for each coverage enhancement (CE) level or for
each group of the coverage enhancement (CE) level.
III-1-2. Collision Between SRS of MTC Device and PUSCH/PUCCH of MTC
Device
A next considerable situation relates to a situation in which the
SRS of the MTC device and the PUSCH/PUCCH of the MTC device collide
with each other. Basically, as the SRS configuration related
parameters (the SRS subframe, the SRS bandwidth, etc.,), types
which are commonly configured with respect to all or some MTC
devices may be considered. Herein, the some MTC devices may be MTC
devices which operate in the same MTC subband.
The MTC device may not map the PUSCH to the last OFDM (SC-FDMA) or
the OFDM (SC-FDMA) symbol in which the SRS may be transmitted (by
the unit of the subframe) according to Condition 1-4 based on the
commonly configured SRS parameters. Whether the last symbol of the
PUSCH is used may be indicated through the higher layer signal. In
more detail, whether the last symbol of the PUSCH is used may be
independently indicated for each coverage enhancement (CE) level or
for each group of the coverage enhancement (CE) level for the SRS
or the PUSCH. In more detail, when the bands in which the SRS and
the PUSCH are transmitted are different from each other, the MTC
device may not transit the PUSCH during a time gap used for
frequency hopping. The time gap may correspond to one OFDM symbol
or multiple OFDM symbols or one slot. For example, the MTC device
may not transmit the PUSCH on two symbols corresponding to a time
section in which the frequency hopping is performed. On the other
hand, the MTC device may transmit the uplink channel while changing
the frequency from a first subband to a second subband. For
example, when the MTC device intends to transmit the PUSCH in the
second band while transmitting the PUCCH in the first subband, the
MTC device may perform RF retuning on first two symbols instead of
transmitting the PUSCH on the first two symbols to which the PUSCH
is mapped. Alternatively, when the MTC device intends to transmit
the PUCCH in the second band while transmitting the PUSCH in the
first subband, the MTC device may perform the RF retuning on last
two symbols instead of transmitting the PUSCH on the last two
symbols to which the PUSCH is mapped. On the other hand, in the
case where one slot is used as the time gap, when the PUSCH and the
SRS are configured to be simultaneously transmitted on the same
subframe, the MTC device may transmit the PUSCH on a first slot and
transmit the SRS on a second slot. In this case, the MTC device may
repeatedly transmit the SRS on the OFDM symbol of the second slot
which remains other than the time required for the frequency
hopping. Through such a method, the base station may prevent the
SRS transmitted by the first MTC device and the PUSCH/PUCCH
transmitted by the second MTC device from colliding with each
other. Alternatively, in a frequency gap section required for the
frequency hopping, the MTC device may drop the transmission of the
SRS or delay the repeated transmission of the SRS. In this case,
the MTC device may transmit the PUCCH/PUSCH with respect to the
last symbol or a region other than the last symbol.
In more detail, in order to support the frequency hopping of the
PUCCH/PUSCH under the condition, even when the frequency hopping is
performed in the subframe just next to the subframe in which the
corresponding PUCCH/PUSCH is transmitted, the MTC device may not
map the PUCCH/PUSCH onto the last OFDM (SC-FDMA) symbol or last
several OFDM (SC-FDMA) symbols or one slot (by the unit of the
subframe). In this case, when the SRS is scheduled to be
transmitted on the subframe in which the frequency hopping is
performed, the MTC device may drop transmission of the
corresponding SRS. The subframe in which the frequency hopping is
performed may be configured according to the higher layer signal or
configured according to a predetermined pattern. As one example,
when the MTC device transmits the PUSCH in subframe n and performs
the frequency hopping in order to change the MTC subband of the MTC
device in subframe n+1, the MTC device may not map the PUCCH/PUSCH
in the last OFDM (SC-FDMA) symbol, last several OFDM symbols, or
one slot of the subframe n. In more detail, the MTC device may not
map the PUCCH/PUSCH onto the multiple OFDM (SC-FDMA) symbols for
the frequency hopping.
Meanwhile, when the MTC device performs a coverage enhancement
operation (e.g., repeated transmission of all or some channels),
the MTC device may unconditionally drop the transmission of the SRS
and map the PUCCH/PUSCH to the corresponding resource. In more
detail, whether the transmission of the SRS is dropped may be
determined according to the higher layer signal from the base
station. The higher layer signal may vary between the PUCCH and the
PUSCH and/or vary for each coverage enhancement (CE) level/each
group of the coverage enhancement (CE) level. The MTC device may
drop the transmission of the SRS only when dropping the
transmission of the SRS by the MTC device is indicated by the
higher layer signal. Further, when the higher layer signal is
received, the MTC device may drop the transmission of the SRS even
in the case where the MTC device does not perform the coverage
enhancement. In more detail, when the MTC device performs the
frequency hopping, the PUCCH/PUSCH may not be mapped onto the last
OFDM (SC-FDMA) symbol (by the unit of the subframe) in the
frequency domain or the time section in which the MTC subband is
performed. In this case, when the frequency hopping is performed
during the time section corresponding to the multiple subframes,
the MTC device may just map the PUCCH/PUSCH to the last OFDM
(SC-FDMA) symbol (by the unit of the subframe) in the frequency
domain or the time section in which the MTC subband is not changed.
Additionally, it may be assumed that the MTC device which operates
in the MTC subband does not transmit the SRS during a time (during
an inconsecutive time section or a consecutive time section) during
which the PUCCH/PUSCH is transmitted. The reason is that it is
difficult for the MTC device to transmit the SRS in a subband other
than the MTC subband in which the PUSCH is transmitted. More
additionally, the MTC device may stop the transmission of the SRS
during a time section in which the MTC device transmits the PUCCH
or PUSCH, during a section in which the MTC device which operates
as half-duplex FDD monitors the PDCCH (that is, M-PDCCH) for the
MTC device, or during a section in which the MTC device receives
data.
When a region to which the PUSCH will not be mapped is designated
according to Condition 1-4 related to the SRS configuration
parameter for the MTC device, the PUSCH may be prevented from being
mapped onto the multiple OFDM (SC-FDMA) symbols for purposes for
enhancement of the SRS, etc. In this case, the MTC device may
transmit the SRS on the corresponding multiple OFDM (SC-FDMA)
symbols.
As another method, only the MTC device may not map the PUSCH/PUCCH
on the last OFDM (SC-FDMA) symbol. The base station may notify that
the MTC device maps the PUSCH/PUCCH on the last OFDM (SC-FDMA)
symbol to the MTC device through the higher layer signal so as to
prevent the MTC device from mapping the PUSCH/PUCCH on the last
OFDM (SC-FDMA) symbol. The higher layer signal may designate a set
of subframes or designate a set of subbands. When the SRS is
transferred to the MTC device through the higher layer signal, the
MTC device may differentiate application according to the higher
layer signal since a predetermined period. Further, the higher
layer signal may notify the mode to the MTC device. When the higher
layer signal is transferred, the MTC device may transmit a general
PUCCH/PUSCH on all subframes (that is, subframes other than the SRS
subframes configured for the MTC device) (it is assumed that this
is notified to the MTC device through an MTC-SIB). Alternatively,
it may be assumed that the MTC device continuously uses the reduced
PUCCH format and it may be assumed that the MTC device is
configured with the set of subframes or the set of subframes and
the set of subbands in which a general PUCCH format may be used
from the base station. When the set of subbands is given, the MTC
device may apply the corresponding configuration only when the
given set of subbands coincides with the set of subbands in which
the PUCCH or PUSCH may be transmitted.
On the other hand, it may be considered that the MTC devices do not
use carrier aggregation (CA) and in this case, Condition 4 may be
excluded from the application among the conditions. Meanwhile, the
PUSCH is primarily described up to now, but the corresponding
description may be applied even in determining whether the reduced
PUCCH format is used. As described above, in the case of the PUCCH,
following conditions may be applied instead of the conditions.
TABLE-US-00007 TABLE 7 Condition 1': The cell-specific SRS should
not be a part of the last SC-FDMA symbol on the configured subframe
Condition 1'': When the bandwidth for transmitting the PUCCH
partially or wholly overlaps with the cell-specific SRS bandwidth,
the cell-specific SRS should not be a part of the last SC-FDMA
symbol on the configured subframe
The method proposed by the present invention can be used in various
schemes as well as in ICIC. For example, the method can be used to
identify the difference between DL timings of multiple serving
cells, and to maintain synchronization of each serving cell. The
reduced PUCCH format according to the condition application may be
used as a case where the simultaneous transmission of the
HARQ-ACK/NACK and the SRS is configured in the higher layer with
respect to the corresponding MTC device or cell or MTC subband.
In more detail, Condition 1' may be applied to the cell-specific or
subband-specific SRS configuration information for the MTC device
using the same MTC subband. In addition, Condition 1'' may be
applied to the remainder (the SRS configuration information for the
legacy UE and/or the cell-specific or subband-specific SRS
configuration information for the MTC devices which operate in
other MTC subbands). Alternatively, when the MTC device does not
perform the SRS transmission (when the MTC device corresponds to a
specific coverage enhancement (CE) level coverage enhancement (CE)
level group), the MTC device may apply Condition 1'' and when the
MTC device performs the SRS transmission, the MTC device may apply
Condition 1'.
In the related art, the reason for allowing the reduced PUCCH
format to be used even when the cell-specific SRS bandwidth and an
actual PUCCH do not overlap with each other is that all UEs in the
cell should be compelled to similarly use the reduced PUCCH format
in order to multiplex the PUCCH transmitted by the corresponding UE
and the PUCCH transmitted by another UE in the cell when even at
least any one legacy UE in the cell uses the reduced PUCCH format
in order to transmit both the PUCCH and the SRS. However, when the
UEs that transmit the SRS and the PUCCH belong to different groups,
if actual or reserved frequency resources do not overlap with each
other, it may be efficient that the base station independently
configures the reduced PUCCH format or not for the UEs in terms of
resource utilization.
The base station may configure whether the MTC device uses the
reduced PUCCH format through the higher layer signal. In more
detail, the base station may configure whether the MTC device uses
the reduced PUCC format through the higher layer signal for the MTC
device independently for each coverage enhancement (CE) level or
each group of the coverage enhancement (CE) level for the SRS or
the PUCCH.
When the base station does not transfer the SRS configuration
information for the legacy UE or when the MTC device does not
configure the subframe to which the PUCCH is to be mapped
(alternatively, not to be mapped) or the section or mode of the
subframes on the last symbol, the MTC device may previously
determine a default operation to be basically applied. The
corresponding default operation may be preventing the MTC device
from continuously mapping the PUSCH on the last symbol or contrary
to this, allowing the MTC device to continuously map the PUSCH. In
more detail, the default operation allows the MTC device to
continuously map the PUSCH on the last symbol, but when the base
station transfers the SRS configuration information for the MTC
device, the MTC device may not map the PUSCH to the last symbol by
referring to the corresponding configuration and the condition.
Next, one example of an operation method for Case A) a case where
the MTC device maps the PUSCH on the last OFDM (SC-FDMA) symbol or
the OFDM (SC-FDMA) symbol in which the SRS may be transmitted, Case
B) a case where the MTC device transits the SRS on the last OFDM
(SC-FDMA) symbol or the OFDM (SC-FDMA) symbol in which the SRS may
be transmitted, and Case C) a case where the MTC device maps
neither the PUSCH nor the SRS on the last OFDM (SC-FDMA) symbol or
the OFDM (SC-FDMA) symbol in which the SRS may be transmitted will
be described.
1) Case A: The Case where the MTC Device Maps the PUSCH on the Last
OFDM (SC-FDMA) Symbol or the OFDM (SC-FDMA) Symbol in which the SRS
May be Transmitted
As a first example, the MTC device maps the UL-SCH to the
corresponding region.
As a second example, the MTC device maps an additional DMRS to the
corresponding region. The additional DMRS may be used for radio
channel estimation for demodulating the PUSCH in addition to the
DMRS already mapped to the PUSCH. Generation of a DMRS sequence may
be performed in the same method as generation of the DMRS sequence
mapped to another OFDM (SC-FDMA) symbol. In more detail, the region
to which the DMRS is mapped may include a region to which the SRS
transmission is mapped. Further, the DMRS sequence may be generated
based on the inclusion of the SRS transmission region. In this
case, the generation of the DMRS sequence may be different from the
method for generating the DMRS sequence mapped to another OFDM
(SC-FDMA) symbol.
As a third example, the MTC device maps an additional SRS to the
corresponding region. The additional SRS may be used for the radio
channel estimation for demodulating the PUSCH in addition to the
DMRS already mapped to the PUSCH. In more detail, the additional
SRS may be transmitted only in an RB (alternatively, frequency
resource) region in which the PUSCH is transmitted. The additional
SRS sequence may be generated based on the SRS configuration for
the corresponding MTC device. In this case, comb may be applied.
Herein, a comb type may be inconsecutively mapping the sequence to
the subcarrier instead of consecutively mapping the sequence to the
subcarrier at the time of mapping the sequence to the subcarrier.
As one example, the sequence may be mapped only to even or odd
indexes and no information may be mapped to residual subcarriers.
Alternatively, the sequence of the additional SRS may be generated
by the same method as the DMRS sequence, but may have a different
sequence length from the DMRS sequence mapped to another OFDM
(SC-FDMA) symbol.
2) Case B: The Case where the MTC Device Transmits the SRS on the
Last OFDM (SC-FDMA) Symbol or the OFDM (SC-FDMA) Symbol in which
the SRS May be Transmitted
As the first example, the MTC device transmits the SRS on the OFDM
(SC-FDMA) symbol. In a region where the frequency resource in which
the SRS is transmitted and the frequency resource in which the
PUSCH is transmitted overlap with each other, it may be considered
that the correspond SRS is used for the radio channel estimation
for demodulating the PUSCH. In more detail, the SRS may be
transmitted on the last OFDM (SC-FDMA) symbol. The sequence of the
SRS may be generated based on the SRS configuration for the
corresponding MTC device. In this case, the comb may be applied.
Alternatively, the SRS sequence may be generated by the same method
as the DMRS sequence. However, the SRS sequence may have a
different length from the DMRS sequence mapped onto another OFDM
(SC-FDMA) symbol.
As the second example, the MTC device maps the DMRS to the
corresponding region. In this case, the MTC device may drop the
transmission of the SRS and transmit the DMRS of the PUSCH instead
of the SRS. The corresponding DMRS may substitute for the SRS in
addition to being used for the radio channel estimation for
demodulating the PUSCH. The generation method of the DMRS sequence
may be the same as that of the DMRS sequence mapped to another OFDM
(SC-FDMA) symbol. In more detail, the region to which the DMRS is
mapped may include the region to which the SRS transmission is
mapped. Further, the DMRS sequence may be generated based on the
inclusion of the SRS transmission region. The DMRS including the
SRS transmission region may correspond to the additional reference
signal (that is, extended DMRS) among the DMRSs for demodulating
the PUSCH. In this case, the generation method of the DMRS
including the SRS transmission region may be different from the
generation method of the DMRS sequence mapped to another OFDM
(SC-FDMA) symbol.
As the third example, the MTC device may determine whether to
transmit the SRS or the DMRS based on a parameter defined by the
frequency resource region in which the SRS is transmitted and the
frequency resource region in which the DMRS is transmitted. As one
example, it may be considered that the MTC device transmits the
reference signal corresponding to a superset of the frequency
resource region. When the region in which the SRS is transmitted
includes the region in which the DMRS is transmitted, the MTC
device may transmit the SRS and in the contrary case, the MTC
device may transmit the DMRS. When the superset does not exist, it
may be considered that the MTC device transmits a separate
reference signal. However, the separate reference signal may be the
DMRS type (the sequence generation method of the DMRS and the
mapping method to the subcarrier) and the SRS type (the sequence
generation method of the SRS and the mapping method to the
subcarrier (including the comb type)).
3) Case C: The Case where the MTC Device Maps Neither the PUSCH Nor
the SRS on the Last OFDM (SC-FDMA) Symbol or the OFDM (SC-FDMA)
Symbol in which the SRS May be Transmitted
The MTC device transmits nothing while the OFDM (SC-FDMA) symbol is
empty as it is. The reason therefor is that another MTC device or
the legacy UE may transmit the SRS in the corresponding region.
As another method, the MTC device may map the SRS to all or some
OFDM (SC-FDMA) symbols in which the DMRS is transmitted. In this
case, the SRS transmitted by the MTC device may be subjected to
code division multiplexing with the DMRS included in the PUSCH of
another legacy UE based on the cyclic shift and/or OCC. To this
end, it may be considered that the base station notifies the cyclic
shift and/or OCC index to the MTC device for each parameter set of
the periodic SRS or the aperiodic SRS for the MTC device. In this
case, it may be considered that a process is omitted, in which the
MTC device maps the PUSCH (and PUCCH) onto the last OFDM (SC-FDMA)
symbol or the OFDM (SC-FDMA) symbol in which the SRS may be
transmitted (by the unit of the subframe) in association with the
SRS of the MTC device. In association with the legacy UE, the
process may be just performed, in which the MTC device maps the
PUSCH (and PUCCH) onto the last OFDM (SC-FDMA) symbol. Herein, the
SRS sequence may be generated in the same method as the DMRS
sequence and the method for mapping the SRS to the subcarrier may
also be the same as the method for mapping the DMRS to the
subcarrier. In this case, the comb type may not be applied. In this
case, by increasing the density of the SRS, channel estimation
performance by the SRS may be enhanced. In more detail, the OFDM
(SC-FDMA) symbol in which the SRS is transmitted may correspond to
the symbol in which the additional reference signal (that is,
extended DMRS) is transmitted among the DMRSs for demodulating the
PUSCH. When the MTC device transmits the SRS in the subframe
without PUSCH transmission, it may be considered that the MTC
device transmits only the SRS on all or some OFDM (SC-FDMA) symbols
to which the DMRS may be mapped and in this case, a collision with
the PUSCH (alternatively, PUCCH) transmitted by another UE may be
divided in the CMD method by the cyclic shift and/or OCC configured
in the DMRS and the SRS. When the MTC device transmits the SRS in
the subframe with the PUSCH transmission, the MTC device may
perform the sequence generation and the RE mapping with respect to
the DMRS on the OFDM (SC-FDMA) symbol other than the OFDM (SC-FDMA)
symbol to which the SRS is to be mapped similarly to the case where
the SRS is not transmitted. In addition, the MTC device may perform
the sequence generation and the RE mapping with respect to the OFDM
(SC-FDMA) symbol to which the SRS is to be mapped by the same
method as the DMRS. In more detail, the length of the sequence and
the RE mapping may be configured differently from the DMRS with
respect to the OFDM (SC-FDMA) symbol to which the SRS is to be
mapped.
As one example, it is assumed that the MTC device maps the PUSCH to
OFDM (SC-FDMA) symbols #0, #3, #7, and #10 based on the normal CP.
Further, it is assumed that the OCC having the length of 4 is
applied to the DMRS which is extended throughout the four symbols
to be divided by the CDM method among the multiple UEs.
The corresponding MTC device may generate the DMRS for demodulating
the PUSCH and perform the RE mapping according to resource
allocation information for the PUSCH and DCI information on the
cyclic shift, etc., in the subframe in which the SRS is not
transmitted. In this case, the DMRS and the SRS of another UE may
be distinguished by the combination of the OCC and the cyclic shift
according to SRS parameters (the SRS bandwidth, the cyclic shift,
the comb index, etc., which may be configured to be
cell-specific/subcarrier-specific/UE-specific) of another UE. As
one example, when N RBs are allocated to the PUSCH, the MTC device
may generate the sequence of the reference signal having the length
of N*Msc (herein, Msc as the number of subcarriers per RB may be
12) and map the DMRS to N RBs to which the corresponding PUSCH is
allocated for the DMRS of the PUSCH.
The corresponding MTC device may additionally generate the DMRS for
demodulating the PUSCH and perform the RE mapping to the DCI
information for the PUSCH based on the SRS parameters of the
corresponding MTC device in the subframe in which the SRS is
transmitted. In this case, the SRSs from the multiple UEs may be
distinguished by the combination of the OCC and the cyclic shift
according to each SRS parameter. As a more detailed example, when
RB allocations are different from each other between the SRSs or
between the SRS and the PUSCH, the RB allocations may be
distinguished by using the OCC and when the RB allocations are the
same as each other, the RB allocations may be distinguished by the
combination of the cyclic shift and/or the OCC. As one example,
when N RBs are allocated to the PUSCH and the SRS is additionally
mapped to K RBs in addition to the N RBs to which the PUSCH is
allocated, and as a result, the SRS is allocated to a total of N+K
RBs, the sequence having the length of N*K*Msc for the DMRS for
demodulating the PUSCH and the sequence may be mapped to N+K RBs.
As another example, when N RBs are allocated to the PUSCH and K RBs
are allocated to the SRS so that the SRS does not overlap with the
PUSCH or the SRS only partially overlaps with the PUSCH, the DMRS
includes all regions to which the SRS and the PUSCH are allocated
and the MTC device generates the sequence of the reference signal
and performs the RE mapping based on a minimum of L RBs so as to
consecutively enable the RE mapping.
The MTC device may generate the DMRS or SRS for demodulating the
PUSCH and perform the RE mapping based on the SRS parameters of the
corresponding MTC device in the subframe in which the corresponding
MTC device transmits the SRS ad does not transmit the PUSCH. As one
example, when the SRS is allocated to K RBs, the MTC device may
generate the sequence having the length of K*Msc for the
corresponding SRS and map the corresponding sequence to the REs on
corresponding K RBs.
III-1-3. Aperiodic SRS Transmission of MTC Device
In a next-generation MTC environment, as the MTC device may operate
only on not the entire system band but a partial subband of the
cell, an RF retuning time for changing the subband or changing a
frequency location may be additionally required when the MTC device
transmits the SRS.
The legacy UE transmits the aperiodic SRS through an aperiodic SRS
resource on the subframe which is earliest since four subframes
since a time triggered by the base station and in some cases, a
time required for retuning the RF may not be secured. In this case,
a timing of transmitting the aperiodic SRS needs to be changed. In
brief, when the MTC device detects triggering of the transmission
of the SRS in subframe n (when receiving a DCI bundle requesting
the transmission of the SRS is completed in the coverage
enhancement (CE) situation), the MTC device may transfer the SRS in
an earliest aperiodic SRS resource since subframe n+4+k. A value of
the k may be 1 or more. However, when the MTC device need not
retune the RF (when retuning the RF is not required for
transmitting the SRS), the value of the k may be 0.
The SRS may be triggered by DCI format 0 (alternatively, DCI format
4) or a DCI (e.g., DCI format 1A, etc.) corresponding to downlink
scheduling and in the case of the coverage enhancement, a
processing method of a collision between the repeated transmission
of the PUSCH and the repeated transmission of the SRS may vary
depending on the DCI format for triggering the SRS. As one example,
when the SRS is triggered through the DCI for uplink scheduling
like DCI format 0, since the timing between the repeated
transmission of the PUSCH and the repeated transmission of the SRS
may be normally aligned, the MTC device may just perform the
repeated transmission of the PUSCH and the repeated transmission of
the aperiodic SRS. On the contrary, when the SRS is triggered
through the DCI for the downlink scheduling, the MTC device may
perform the repeated transmission of the SRS while performing the
repeated transmission of the PUSCH which starts before transmitting
the SRS. Alternatively, the MTC device may transmit the SRS through
the aperiodic SRS resource since the repeated transmission of the
PUSCH which is performed ends. As another method, when the
aperiodic SRS is triggered through the DCI format corresponding to
the downlink scheduling, the corresponding DCI may schedule only
the SRS without scheduling the PUSCH. As a more detailed example,
when the MTC device receives the DCI format (e.g., DCI format 0)
for the uplink scheduling and the value of a field for requesting
the aperiodic CSI in the corresponding DCI is 1 (alternatively,
when the value of the field is not 0), the MTC device may interpret
that the corresponding DCI includes not information for scheduling
the PUSCH but only scheduling information for transmitting the SRS.
For example, when a resource allocation field in the DCI is set to
a value indicating one RB in the subband, the MTC device may
transmit the SRS through one corresponding RB at the corresponding
transmission time. The corresponding transmission time may
correspond to an earliest SRS resource since a specific number of
subframes (e.g., 4+k based on the FDD, herein, k is 0 or 1 or 2 by
considering the RF retuning) since the MTC device receives the DCI.
Meanwhile, the MTC device even information on the number of
repetition times/coverage enhancement level, the subband, etc.,
included in the DCI as information for the SRS. When the MTC device
transmits only the SRS, the MTC device may disregard a PUSCH
hopping flag in the information on the PUSCH in the DCI and
interpret the value of the PUSCH hopping flag as a part of the
resource allocation field. In detail, when a pattern for the SRS is
received through the higher layer signal, the MTC device may
perform the repeated transmission of the SRS with the frequency
hopping according to the PUSCH hopping flag. Alternatively, when
the set of subbands in which the SRS is to be transmitted is
received through the higher layer signal, the PUSCH hopping flag
may designate which subband the MTC device reports or how many sets
the MTC device reports.
As another of the DCI interpretation, residual fields other than
the aperiodic SRS field in the DCI may have a value of a
predetermined pattern type and in this case, the MTC device may
determine whether the DCI for the uplink scheduling schedules the
PUSCH transmission or only the SRS transmission based on the
corresponding patterns. Alternatively, when the DCI for the uplink
scheduling satisfies a predetermined combination, the higher layer
signal may designate whether the DCI indicates reporting the
aperiodic CSI or transmitting the aperiodic SRS.
Alternatively, the aperiodic SRS may be triggered together with the
downlink scheduling. This may correspond to only the TDD or full
duplex communicatable FDD. In the case of half-duplex
communication, when the aperiodic SRS is triggered together with
the downlink scheduling, the MTC device may transmit the SRS since
receiving downlink data. This may mean that the transmission of the
PUCCH may be delayed or dropped.
When the MTC device is triggered to transmit the aperiodic SRS, the
MTC device may indicate the subband or frequency location to
transmit the SRS through the configuration for the SRS of the MTC
device or directly notify the location of the subband itself to the
MTC device. However, in order to allow the MTC device to
dynamically select the region to transmit the SRS, the base station
may extend the SRS request field in the DCI to be transmitted to 2
bits or more. The format of the DCI including the SRS request field
extended to 2 bits or more may be DCI format 0, 1A, etc. In this
case, the base station may transmit the corresponding DCI only in a
UE-specific search space (USS). The MTC device may more dynamically
control an SRS transmission location according to the SRS request
field extended to 2 bits or more, which is included in the DCI. As
one example, when the SRS request field in the DCI is extended to 2
bits, the SRS request field may include a parameter associated with
the frequency domain in which the SRS may be transmitted. Further,
when the MTC device performs the repeated transmission of the SRS
with the coverage enhancement, the extended SRS request field in
the DCI may include the number of repeated transmission times of
the SRS or the coverage enhancement level.
IV. Application of OCC to Data Region
In a next MTC system, for the coverage enhancement, it may be
introduced that the base station and the MTC device repeatedly
transmit all or some channels. The repetition may be performed by
the unit of the subframe. In this case, when a channel environment
is not good, it may be inefficient that multiple MTC devices share
the PUSCH resource with each other by depending on only the CDM
method for the DMRS and as a method for reducing the inefficiency,
application of a CDM technique using the OCC, etc., even to the
region (a region to which the UL-SCH and/or CQI/PMI is mapped)
other than the DMRS may be considered.
In brief, it may be considered that the OCC sequence is allocated
and applied to the multiple subframes/slots. As one example, when
the length of the OCC is M, all values finally mapped into the
corresponding subframe/slot may be multiplied by one value of the
corresponding OCC sequence by mapping respective values
constituting the OCC sequence one to one for each subframe/slot in
M subframes/slots. As a more detailed embodiment, when the OCC
sequence is [1 -1], values mapped to all REs of a first
subframe/slot are multiplied by 1 and values mapped to all REs of a
second subframe/slot may be multiplied by -1 with respect to two
subframes/slots. The RE may be excluded from all of the REs.
Basically, in order to apply the OCC, since the values mapped to
all of the REs of the subframe/slot as long as the length of the
OCC (before the application of the OCC) need to be the same as each
other (by the unit of the subframe/slot), it may be considered that
the values are mapped to be the same as each other. However, when
the number of subframes/slots to which the same OCC sequence is to
be applied increases, an orthogonal characteristic may be
alleviated or broken due to a characteristic in which a radio
channel environment temporally varies, it may be considered that
the OCC sequence is applied by the unit of a predetermined level of
M subframes/slots. The value of the M may be 3 or 4.
The embodiments of the present invention which has been described
up to now may be implemented through various means. For example,
the embodiments of the present invention may be implemented by
hardware, firmware, software, or combinations thereof. In detail,
the embodiments will be descried with reference to the
drawings.
FIG. 18 is a Block Diagram Illustrating a Wireless Communication
System in which the Disclosure of the Present Invention is
Implemented.
A base station 200 includes a processor 201, a memory 202, and a
radio frequency (RF) unit 203. The memory 202 is connected with the
processor 201 to store various pieces of information for driving
the processor 201. The RF unit 203 is connected with the processor
201 to transmit and/or receive a radio signal. The processor 201
implements a function, a process, and/or a method which are
proposed. In the aforementioned embodiment, the operation of the
base station may be implemented by the processor 201.
A UE 100 includes a processor 101, a memory 102, and an RF unit
103. The memory 102 is connected with the processor 101 to store
various pieces of information for driving the processor 101. The RF
unit 103 is connected with the processor 101 to transmit and/or
receive a radio signal. The processor 101 implements a function, a
process, and/or a method which are proposed.
The processor may include an application-specific integrated
circuit (ASIC), another chip set, a logic circuit and/or a data
processing apparatus. The memory may include a read-only memory
(ROM), a random access memory (RAM), a flash memory, a memory card,
a storage medium, and/or other storage device. The RF unit may
include a baseband circuit for processing the radio signal. When
the embodiment is implemented by software, the aforementioned
technique may be implemented by a module (a process, a function,
and the like) that performs the aforementioned function. The module
may be stored in the memory and executed by the processor. The
memory may be positioned inside or outside the processor and
connected with the processor by various well-known means.
In the aforementioned exemplary system, methods have been described
based on flowcharts as a series of steps or blocks, but the methods
are not limited to the order of the steps of the present invention
and any step may occur in a step or an order different from or
simultaneously as the aforementioned step or order. Further, it can
be appreciated by those skilled in the art that steps shown in the
flowcharts are not exclusive and other steps may be included or one
or more steps do not influence the scope of the present invention
and may be deleted.
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